id string | uri string | uuid string | version string | status string | trust string | title string | statement string | kind string | domain string | about list | level_band list | locale string | evidence_patterns list | discriminators unknown | relations unknown | alignments list | provenance dict | history dict | license string | reviews list | notes string |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
math.decimals.longer-is-larger | https://open-misconceptions.github.io/miscon-data/m/math.decimals.longer-is-larger | b9976592-9045-4327-8b17-485c7114d359 | 0.1.1 | draft | low | Longer decimal is larger | A decimal with more digits after the point is a larger number, because the digits after the point make a bigger whole number. | overgeneralization | math.decimals | [
{
"scheme": "CCSS",
"code": "4.NF.C.7",
"uri": "http://corestandards.org/Math/Content/4/NF/C/7/"
},
{
"scheme": "CCSS",
"code": "5.NBT.A.3",
"uri": "http://corestandards.org/Math/Content/5/NBT/A/3/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "compare two decimals where the shorter is larger",
"signature": "chooses the decimal with more digits after the point",
"example": {
"item": "Which is larger, 0.5 or 0.25?",
"expected": "0.5",
"response": "0.25"
}
},
{
"item_shape": "order decimals of diffe... | {
"vs_slip": "A slip is one wrong comparison. The belief is diagnosed by a consistent pattern on length-incongruent items and a justification such as 'twenty-five is more than five'.",
"vs": {
"math.decimals.shorter-is-larger": "Mirror belief. Include items where the longer decimal is larger (0.75 vs 0.8): long... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/4/NF/C/7/",
"label": "CCSS 4.NF.C.7: compare two decimals to hundredths by reasoning about their size"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/4/NF/C/7/",
"label": "CCS... | [
{
"scheme": "CCSS",
"code": "4.NF.C.7",
"uri": "http://corestandards.org/Math/Content/4/NF/C/7/",
"relation": "about"
},
{
"scheme": "CCSS",
"code": "5.NBT.A.3",
"uri": "http://corestandards.org/Math/Content/5/NBT/A/3/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Resnick, L. B., Nesher, P., Leonard, F., Magone, M., Omanson, S., & Peled, I. (1989). Conceptual bases of arithmetic errors: The case of decimal fractions. Journal for Research in Mathematics Education, 20(1), 8-27.",
"doi": "10.5951/jresematheduc.2... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.decimals.shorter-is-larger | https://open-misconceptions.github.io/miscon-data/m/math.decimals.shorter-is-larger | e3685617-2ee2-41c1-875f-5e0d835be18f | 0.1.1 | draft | low | Shorter decimal is larger | A decimal with fewer digits after the point is a larger number, because more digits mean smaller pieces, like a fraction with a bigger denominator. | misapplied-analogy | math.decimals | [
{
"scheme": "CCSS",
"code": "4.NF.C.7",
"uri": "http://corestandards.org/Math/Content/4/NF/C/7/"
},
{
"scheme": "CCSS",
"code": "5.NBT.A.3",
"uri": "http://corestandards.org/Math/Content/5/NBT/A/3/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "compare two decimals where the longer decimal is larger",
"signature": "chooses the decimal with fewer digits after the point",
"example": {
"item": "Which is larger, 0.85 or 0.8?",
"expected": "0.85",
"response": "0.8"
},
"notes": "Length-incongruent item; a l... | {
"vs_slip": "Consistent preference for the shorter decimal on length-incongruent items, with a fraction-based justification ('hundredths are smaller than tenths').",
"vs": {
"math.decimals.longer-is-larger": "Mirror belief; use items of both congruence types to separate them."
}
} | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/4/NF/C/7/",
"label": "CCSS 4.NF.C.7: compare two decimals to hundredths by reasoning about their size"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/4/NF/C/7/",
"label": "CCS... | [
{
"scheme": "CCSS",
"code": "4.NF.C.7",
"uri": "http://corestandards.org/Math/Content/4/NF/C/7/",
"relation": "about"
},
{
"scheme": "CCSS",
"code": "5.NBT.A.3",
"uri": "http://corestandards.org/Math/Content/5/NBT/A/3/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Resnick, L. B., Nesher, P., Leonard, F., Magone, M., Omanson, S., & Peled, I. (1989). Conceptual bases of arithmetic errors: The case of decimal fractions. Journal for Research in Mathematics Education, 20(1), 8-27.",
"doi": "10.5951/jresematheduc.2... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.add-across | https://open-misconceptions.github.io/miscon-data/m/math.fractions.add-across | 20f1dd60-ea8a-4e14-ab41-12addc94b751 | 1.1.0 | reviewed | high | Adding fractions across numerators and denominators | Fractions are added by adding the numerators together and adding the denominators together. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "5.NF.A.1",
"uri": "http://corestandards.org/Math/Content/5/NF/A/1/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "add two fractions with unlike denominators",
"signature": "response numerator = a + c and response denominator = b + d for a/b + c/d, with no attempt at a common denominator",
"example": {
"item": "1/2 + 1/3",
"expected": "5/6",
"response": "2/5"
},
"notes": "S... | {
"vs_slip": "A slip appears on one item and not on the next of the same shape, and the learner self-corrects when asked to check with a diagram or with 1/2 + 1/2. A holder of this belief applies the rule consistently across unlike- and like-denominator items and defends 1/2 + 1/2 = 2/4 as correct.",
"vs": {
"m... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/5/NF/A/1/",
"label": "CCSS 5.NF.A.1: add and subtract fractions with unlike denominators"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/5/NF/A/1/",
"label": "CCSS 5.NF.A.1: a... | [
{
"scheme": "CCSS",
"code": "5.NF.A.1",
"uri": "http://corestandards.org/Math/Content/5/NF/A/1/",
"relation": "about",
"note": "Add and subtract fractions with unlike denominators by replacing given fractions with equivalent fractions. CASE Network GUID for this item to be added when the CASE Ne... | {
"sources": [
{
"type": "paper",
"citation": "Brown, J. S., & VanLehn, K. (1980). Repair theory: A generative theory of bugs in procedural skills. Cognitive Science, 4(4), 379-426.",
"doi": "10.1207/s15516709cog0404_3",
"note": "Frames systematic errors as stable procedural bugs, distinct... | {
"changelog": [
{
"version": "1.0.0",
"date": "2026-09-05T00:00:00",
"change": "Initial record."
},
{
"version": "1.1.0",
"date": "2026-09-05T00:00:00",
"change": "Statement trimmed to the belief; likely origins moved to notes; about scheme relabelled CCSS; review repl... | CC-BY-4.0 | [
{
"kind": "human",
"by": "Vikram Maram (github:vikram-learnco)",
"date": "2026-09-05",
"scope": [
"statement",
"evidence",
"discriminators",
"sources"
],
"verdict": "accept",
"notes": "Reviewed in session against the design worked example; statement trimmed to the... | Likely origins: whole-number bias (numerator and denominator treated as independent whole numbers) and overgeneralisation from the multiplication rule. |
math.fractions.add-numerators-keep-denominator | https://open-misconceptions.github.io/miscon-data/m/math.fractions.add-numerators-keep-denominator | 434a29b0-8c52-4db3-a2d6-81c86e5e5d6c | 0.1.1 | draft | low | Adding numerators and keeping one denominator | To add fractions you add the numerators and keep the denominator, whichever denominator is written, because the denominator is just a label that does not take part in the sum. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "5.NF.A.1",
"uri": "http://corestandards.org/Math/Content/5/NF/A/1/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "add two fractions with unlike denominators",
"signature": "response numerator = a + c; response denominator is one of the given denominators (usually the first or the larger), with no conversion of the addends",
"example": {
"item": "1/2 + 1/3",
"expected": "5/6",
"res... | {
"vs_slip": "Consistent across unlike-denominator items; the learner can state the rule (\"the bottom stays\") when asked.",
"vs": {
"math.fractions.add-across": "Give a like-denominator item. This belief answers 1/4 + 2/4 = 3/4 correctly; add-across gives 3/8."
}
} | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/5/NF/A/1/",
"label": "CCSS 5.NF.A.1: add and subtract fractions with unlike denominators"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/5/NF/A/1/",
"label": "CCSS 5.NF.A.1: a... | [
{
"scheme": "CCSS",
"code": "5.NF.A.1",
"uri": "http://corestandards.org/Math/Content/5/NF/A/1/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Ashlock, R. B. (2010). Error Patterns in Computation: Using Error Patterns to Help Each Student Learn (10th ed.). Allyn & Bacon."
},
{
"type": "paper",
"citation": "Ni, Y., & Zhou, Y.-D. (2005). Teaching and learning fraction and ration... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.add-whole-to-numerator | https://open-misconceptions.github.io/miscon-data/m/math.fractions.add-whole-to-numerator | 692fc169-3842-429b-bf5a-36be6eb6e910 | 0.1.1 | draft | low | Adding a whole number to the numerator | To add a whole number and a fraction you add the whole number to the numerator. | procedural-bug | math.fractions | [
{
"scheme": "CCSS",
"code": "4.NF.B.3",
"uri": "http://corestandards.org/Math/Content/4/NF/B/3/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "add a whole number and a proper fraction",
"signature": "adds the whole number to the numerator and keeps the denominator",
"example": {
"item": "2 + 1/3 = ?",
"expected": "2 1/3 (= 7/3)",
"response": "3/3 (= 1)"
}
}
] | {
"vs_slip": "The result is smaller than the whole-number addend and the learner accepts it, consistently. A slip is not repeated across items.",
"vs": {
"math.fractions.mixed-to-improper-add-all": "That bug adds all three numbers when converting a mixed number; this one appears when a whole number and fraction... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/4/NF/B/3/",
"label": "CCSS 4.NF.B.3: understand a fraction a/b with a > 1 as a sum of fractions 1/b"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/4/NF/B/3/",
"label": "CCSS ... | [
{
"scheme": "CCSS",
"code": "4.NF.B.3",
"uri": "http://corestandards.org/Math/Content/4/NF/B/3/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Ashlock, R. B. (2010). Error Patterns in Computation: Using Error Patterns to Help Each Student Learn (10th ed.). Allyn & Bacon."
},
{
"type": "book",
"citation": "Kerslake, D. (1986). Fractions: Children's Strategies and Errors. NFER-N... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.bigger-denominator-bigger-fraction | https://open-misconceptions.github.io/miscon-data/m/math.fractions.bigger-denominator-bigger-fraction | 1288d189-d36c-4a7d-925d-62c88196a161 | 0.1.1 | draft | low | Bigger denominator means bigger fraction | The fraction with the bigger denominator is the bigger fraction, because the denominator is a bigger number. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "3.NF.A.3",
"uri": "http://corestandards.org/Math/Content/3/NF/A/3/"
},
{
"scheme": "CCSS",
"code": "4.NF.A.2",
"uri": "http://corestandards.org/Math/Content/4/NF/A/2/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "compare two unit fractions",
"signature": "picks the unit fraction with the larger denominator as larger; on 1/b vs 1/d chooses the one with the larger b",
"example": {
"item": "Which is larger, 1/3 or 1/8?",
"expected": "1/3",
"response": "1/8"
}
},
{
"ite... | {
"vs_slip": "A slip is a single reversed choice among otherwise correct comparisons. The belief shows as a consistent preference for the larger denominator across unit-fraction items and a justification such as 'eight is more than three'.",
"vs": {
"math.fractions.compare-whole-number-components": "Use an item... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/3/NF/A/3/",
"label": "CCSS 3.NF.A.3: explain equivalence of fractions and compare fractions by reasoning about their size"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/3/NF/A/1/",... | [
{
"scheme": "CCSS",
"code": "3.NF.A.3",
"uri": "http://corestandards.org/Math/Content/3/NF/A/3/",
"relation": "about"
},
{
"scheme": "CCSS",
"code": "4.NF.A.2",
"uri": "http://corestandards.org/Math/Content/4/NF/A/2/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Stafylidou, S., & Vosniadou, S. (2004). The development of students' understanding of the numerical value of fractions. Learning and Instruction, 14(5), 503-518.",
"doi": "10.1016/j.learninstruc.2004.06.015",
"note": "Reports the 'fraction inc... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.cancel-matching-digits | https://open-misconceptions.github.io/miscon-data/m/math.fractions.cancel-matching-digits | 9b81e6e0-ad37-42aa-9494-bc6892e7140b | 0.1.1 | draft | low | Cancelling matching digits | A fraction is simplified by crossing out a digit that appears in both the numerator and the denominator. | notation-confusion | math.fractions | [
{
"scheme": "CCSS",
"code": "4.NF.A.1",
"uri": "http://corestandards.org/Math/Content/4/NF/A/1/"
}
] | [
"middle",
"secondary"
] | en | [
{
"item_shape": "simplify a fraction whose numerator and denominator share a digit",
"signature": "deletes the shared digit from both numbers",
"example": {
"item": "Simplify 12/24",
"expected": "1/2",
"response": "1/4 (cancelling the 2s)"
},
"notes": "16/64 = 1/4 and 19/95 = 1... | {
"vs_slip": "Ask the learner to simplify 16/64 and then 12/24 and explain. The belief is 'the sixes cancel'; a slip has no digit-based rule.",
"vs": {
"math.fractions.equivalence-additive": "Additive reasoners subtract from both parts; digit cancellers delete a digit and leave the rest."
}
} | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/4/NF/A/1/",
"label": "CCSS 4.NF.A.1: explain why a fraction a/b is equivalent to (n x a)/(n x b)"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/4/NF/A/1/",
"label": "CCSS 4.N... | [
{
"scheme": "CCSS",
"code": "4.NF.A.1",
"uri": "http://corestandards.org/Math/Content/4/NF/A/1/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Ashlock, R. B. (2010). Error Patterns in Computation: Using Error Patterns to Help Each Student Learn (10th ed.). Allyn & Bacon."
},
{
"type": "paper",
"citation": "Brown, J. S., & VanLehn, K. (1980). Repair theory: A generative theory ... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.compare-by-gap | https://open-misconceptions.github.io/miscon-data/m/math.fractions.compare-by-gap | c2797bf8-5aff-4019-98c3-3462a3c42f71 | 0.1.1 | draft | low | Comparing fractions by the gap between numerator and denominator | The size of a fraction is decided by how many pieces are missing from the whole; fractions with the same gap between numerator and denominator are equal. | misapplied-analogy | math.fractions | [
{
"scheme": "CCSS",
"code": "4.NF.A.2",
"uri": "http://corestandards.org/Math/Content/4/NF/A/2/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "compare two fractions with the same numerator-denominator gap",
"signature": "declares the fractions equal because each is the same number of pieces short of one whole",
"example": {
"item": "Which is larger, 5/6 or 7/8?",
"expected": "7/8",
"response": "They are the s... | {
"vs_slip": "Ask the learner to explain. Gap thinkers say 'both are one away from a whole' or 'this one is closer'. A slip comes with no such rule and is not repeated on 3/4 vs 9/10.",
"vs": {
"math.fractions.compare-whole-number-components": "On 5/6 vs 7/8 component comparison picks 7/8; gap thinking says equ... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/4/NF/A/2/",
"label": "CCSS 4.NF.A.2: compare two fractions with different numerators and different denominators"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/3/NF/A/3/",
"la... | [
{
"scheme": "CCSS",
"code": "4.NF.A.2",
"uri": "http://corestandards.org/Math/Content/4/NF/A/2/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Pearn, C., & Stephens, M. (2004). Why you have to probe to discover what Year 8 students really think about fractions. In I. Putt, R. Faragher & M. McLean (Eds.), Mathematics Education for the Third Millennium: Towards 2010 (Proceedings of MERGA 27, pp. 4... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.compare-whole-number-components | https://open-misconceptions.github.io/miscon-data/m/math.fractions.compare-whole-number-components | 210d5db3-daa8-49be-aaf9-aa453ea6b234 | 0.1.1 | draft | low | Comparing fractions by their whole-number parts | To compare two fractions you compare the numerators and the denominators as whole numbers; a fraction with bigger numbers is a bigger fraction. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "4.NF.A.2",
"uri": "http://corestandards.org/Math/Content/4/NF/A/2/"
}
] | [
"primary",
"middle",
"secondary"
] | en | [
{
"item_shape": "compare two fractions where the larger fraction has the smaller numerator and denominator",
"signature": "chooses the fraction whose numerator and denominator are both larger",
"example": {
"item": "Which is larger, 4/5 or 5/9?",
"expected": "4/5",
"response": "5/9"
... | {
"vs_slip": "Compare accuracy on congruent and incongruent items. A holder of this belief is near-perfect on congruent items and systematically wrong on incongruent ones; a slip does not follow that split.",
"vs": {
"math.fractions.bigger-denominator-bigger-fraction": "Unit-fraction items isolate the denominat... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/4/NF/A/2/",
"label": "CCSS 4.NF.A.2: compare two fractions with different numerators and different denominators"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/3/NF/A/3/",
"la... | [
{
"scheme": "CCSS",
"code": "4.NF.A.2",
"uri": "http://corestandards.org/Math/Content/4/NF/A/2/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Obersteiner, A., Van Dooren, W., Van Hoof, J., & Verschaffel, L. (2013). The natural number bias and magnitude representation in fraction comparison by expert mathematicians. Learning and Instruction, 28, 64-72.",
"doi": "10.1016/j.learninstruc.2013... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.cross-multiply-to-multiply | https://open-misconceptions.github.io/miscon-data/m/math.fractions.cross-multiply-to-multiply | fef262fa-6980-416d-bd92-851b64e59458 | 0.1.1 | draft | low | Cross-multiplying to multiply fractions | To multiply two fractions you multiply diagonally: the first numerator by the second denominator over the first denominator by the second numerator. | procedural-bug | math.fractions | [
{
"scheme": "CCSS",
"code": "5.NF.B.4",
"uri": "http://corestandards.org/Math/Content/5/NF/B/4/"
}
] | [
"middle",
"secondary"
] | en | [
{
"item_shape": "multiply two proper fractions",
"signature": "product numerator = a x d and product denominator = b x c for a/b x c/d",
"example": {
"item": "2/3 x 4/5 = ?",
"expected": "8/15",
"response": "10/12"
}
}
] | {
"vs_slip": "Consistent across items and usually accompanied by the word 'cross-multiply'. A slip is one diagonal product.",
"vs": {
"math.fractions.multiply-with-common-denominator": "Common-denominator multipliers show a conversion step in their working; cross-multipliers do not."
}
} | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/5/NF/B/4/",
"label": "CCSS 5.NF.B.4: multiply a fraction or whole number by a fraction"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/5/NF/B/4/",
"label": "CCSS 5.NF.B.4: mul... | [
{
"scheme": "CCSS",
"code": "5.NF.B.4",
"uri": "http://corestandards.org/Math/Content/5/NF/B/4/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Ashlock, R. B. (2010). Error Patterns in Computation: Using Error Patterns to Help Each Student Learn (10th ed.). Allyn & Bacon."
},
{
"type": "paper",
"citation": "Newton, K. J. (2008). An extensive analysis of preservice elementary te... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.divide-larger-by-smaller | https://open-misconceptions.github.io/miscon-data/m/math.fractions.divide-larger-by-smaller | 78a649f3-688d-49a2-a85c-7be491860757 | 0.1.1 | draft | low | You can only divide a larger number by a smaller one | In a division the bigger number must be divided by the smaller number, so if the divisor is bigger the two numbers should be swapped. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "6.NS.A.1",
"uri": "http://corestandards.org/Math/Content/6/NS/A/1/"
}
] | [
"primary",
"middle",
"adult"
] | en | [
{
"item_shape": "divide a fraction by a larger whole number",
"signature": "swaps dividend and divisor so that the larger number is divided by the smaller",
"example": {
"item": "1/2 / 3 = ?",
"expected": "1/6",
"response": "6"
}
},
{
"item_shape": "write the division for a... | {
"vs_slip": "A slip is one reversed pair. The belief is a stated rule ('you can't divide a small number by a big one') and is applied to whole numbers too (3 / 12 rewritten as 12 / 3).",
"vs": {
"math.fractions.divide-makes-smaller": "Divide-makes-smaller keeps the order and gets a smaller wrong result; this b... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/6/NS/A/1/",
"label": "CCSS 6.NS.A.1: interpret and compute quotients of fractions"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/6/NS/A/1/",
"label": "CCSS 6.NS.A.1: interpre... | [
{
"scheme": "CCSS",
"code": "6.NS.A.1",
"uri": "http://corestandards.org/Math/Content/6/NS/A/1/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Fischbein, E., Deri, M., Nello, M. S., & Marino, M. S. (1985). The role of implicit models in solving verbal problems in multiplication and division. Journal for Research in Mathematics Education, 16(1), 3-17.",
"doi": "10.5951/jresematheduc.16.1.00... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.divide-makes-smaller | https://open-misconceptions.github.io/miscon-data/m/math.fractions.divide-makes-smaller | 72884d31-1a9a-418f-92ee-f073eef02008 | 0.1.1 | draft | low | Division always makes smaller | Dividing always gives a result smaller than the number you started with, so dividing by a fraction cannot make a number bigger. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "5.NF.B.7",
"uri": "http://corestandards.org/Math/Content/5/NF/B/7/"
},
{
"scheme": "CCSS",
"code": "6.NS.A.1",
"uri": "http://corestandards.org/Math/Content/6/NS/A/1/"
}
] | [
"primary",
"middle",
"secondary",
"adult"
] | en | [
{
"item_shape": "predict whether a quotient will be larger or smaller than the dividend, without calculating",
"signature": "predicts the quotient of a number divided by a proper fraction is smaller than the number",
"example": {
"item": "Without calculating, is 6 / 1/2 more or less than 6?",
... | {
"vs_slip": "A slip is one wrong prediction. The belief is stated as a rule ('dividing makes it smaller') and holds for decimals too; it often coexists with math.fractions.multiply-makes-bigger.",
"vs": {
"math.fractions.multiply-makes-bigger": "Mirror belief; test each separately.",
"math.fractions.invert... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/5/NF/B/7/",
"label": "CCSS 5.NF.B.7: divide unit fractions by whole numbers and whole numbers by unit fractions"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/5/NF/B/7/",
"la... | [
{
"scheme": "CCSS",
"code": "5.NF.B.7",
"uri": "http://corestandards.org/Math/Content/5/NF/B/7/",
"relation": "about"
},
{
"scheme": "CCSS",
"code": "6.NS.A.1",
"uri": "http://corestandards.org/Math/Content/6/NS/A/1/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Fischbein, E., Deri, M., Nello, M. S., & Marino, M. S. (1985). The role of implicit models in solving verbal problems in multiplication and division. Journal for Research in Mathematics Education, 16(1), 3-17.",
"doi": "10.5951/jresematheduc.16.1.00... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.division-is-sharing-only | https://open-misconceptions.github.io/miscon-data/m/math.fractions.division-is-sharing-only | 50e4d120-cd01-49b2-95e6-5ec8df0762d1 | 0.1.1 | draft | low | Division of fractions only means sharing | Dividing means sharing a quantity equally among a number of people, so a division by a fraction has no meaning and must be a mistake or a different operation. | undergeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "6.NS.A.1",
"uri": "http://corestandards.org/Math/Content/6/NS/A/1/"
},
{
"scheme": "CCSS",
"code": "5.NF.B.7",
"uri": "http://corestandards.org/Math/Content/5/NF/B/7/"
}
] | [
"primary",
"middle",
"adult"
] | en | [
{
"item_shape": "choose the operation for a measurement-division word problem",
"signature": "rejects division and multiplies or divides by the wrong number, because 'you can't share among half a person'",
"example": {
"item": "How many 1/2-cup servings are in 3 cups?",
"expected": "3 / 1/2 ... | {
"vs_slip": "A slip is one wrong operation choice. The belief is revealed when the learner is asked to model or explain division and only ever produces sharing stories.",
"vs": {
"math.fractions.divide-makes-smaller": "Divide-makes-smaller computes an answer with the wrong direction; this belief refuses or rei... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/6/NS/A/1/",
"label": "CCSS 6.NS.A.1: interpret and compute quotients of fractions"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/6/NS/A/1/",
"label": "CCSS 6.NS.A.1: interpre... | [
{
"scheme": "CCSS",
"code": "6.NS.A.1",
"uri": "http://corestandards.org/Math/Content/6/NS/A/1/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Fischbein, E., Deri, M., Nello, M. S., & Marino, M. S. (1985). The role of implicit models in solving verbal problems in multiplication and division. Journal for Research in Mathematics Education, 16(1), 3-17.",
"doi": "10.5951/jresematheduc.16.1.00... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.equivalence-additive | https://open-misconceptions.github.io/miscon-data/m/math.fractions.equivalence-additive | 5aadfc6d-33f3-4336-908b-02c278e40508 | 0.1.1 | draft | low | Equivalent fractions by adding the same number | You get an equivalent fraction by adding the same number to the numerator and the denominator, or by subtracting the same number from both. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "4.NF.A.1",
"uri": "http://corestandards.org/Math/Content/4/NF/A/1/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "complete an equivalent fraction with a given denominator",
"signature": "adds the difference in denominators to the numerator",
"example": {
"item": "2/3 = ?/6",
"expected": "4/6",
"response": "5/6"
}
},
{
"item_shape": "simplify a fraction",
"signature... | {
"vs_slip": "Consistent across items; the learner defends it as 'you have to do the same to both'. A slip is a single wrong numerator with multiplicative reasoning elsewhere.",
"vs": {
"math.fractions.cancel-matching-digits": "Digit cancellers only act when a digit repeats (16/64); additive reasoners act on an... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/4/NF/A/1/",
"label": "CCSS 4.NF.A.1: explain why a fraction a/b is equivalent to (n x a)/(n x b)"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/4/NF/A/1/",
"label": "CCSS 4.N... | [
{
"scheme": "CCSS",
"code": "4.NF.A.1",
"uri": "http://corestandards.org/Math/Content/4/NF/A/1/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Hart, K. M. (Ed.). (1981). Children's Understanding of Mathematics: 11-16. John Murray. (Concepts in Secondary Mathematics and Science project.)",
"note": "CSMS: additive strategies on equivalence items."
},
{
"type": "book",
"cit... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.fraction-decimal-digit-copy | https://open-misconceptions.github.io/miscon-data/m/math.fractions.fraction-decimal-digit-copy | fb3c3db0-26d5-4aba-a7ea-c9ce84089d88 | 0.1.1 | draft | low | Writing a fraction as a decimal by copying its digits | A fraction is written as a decimal by putting its numerator, or its denominator, after the decimal point. | notation-confusion | math.fractions | [
{
"scheme": "CCSS",
"code": "4.NF.C.6",
"uri": "http://corestandards.org/Math/Content/4/NF/C/6/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "convert a unit fraction to a decimal",
"signature": "writes 0.<denominator>",
"example": {
"item": "Write 1/4 as a decimal",
"expected": "0.25",
"response": "0.4"
}
},
{
"item_shape": "convert a decimal to a fraction",
"signature": "writes the digits af... | {
"vs_slip": "Consistent across fractions, and the learner cannot say whether 0.4 and 1/4 are the same size. A slip is one wrong conversion with correct ones nearby."
} | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/4/NF/C/6/",
"label": "CCSS 4.NF.C.6: use decimal notation for fractions with denominators 10 or 100"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/4/NF/C/6/",
"label": "CCSS ... | [
{
"scheme": "CCSS",
"code": "4.NF.C.6",
"uri": "http://corestandards.org/Math/Content/4/NF/C/6/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Kerslake, D. (1986). Fractions: Children's Strategies and Errors. NFER-Nelson."
},
{
"type": "paper",
"citation": "Markovits, Z., & Sowder, J. T. (1991). Students' understanding of the relationship between fractions and decimals. Focus ... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.improper-impossible | https://open-misconceptions.github.io/miscon-data/m/math.fractions.improper-impossible | 5211ad46-cba5-4c3d-92ff-9fa79d9ed753 | 0.1.1 | draft | low | A fraction cannot be more than one whole | A fraction is always part of one whole, so the numerator can never be bigger than the denominator and a fraction can never be greater than 1. | undergeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "4.NF.B.3",
"uri": "http://corestandards.org/Math/Content/4/NF/B/3/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "add two proper fractions whose sum exceeds one",
"signature": "adjusts the result so it stays below or equal to one",
"example": {
"item": "3/4 + 3/4 = ?",
"expected": "6/4 (= 1 1/2)",
"response": "6/8 (or 1)"
}
},
{
"item_shape": "place an improper fractio... | {
"vs_slip": "Ask directly whether 7/4 is a number. A slip is an arithmetic error; the belief is the stated rule 'the top can't be bigger than the bottom'.",
"vs": {
"math.fractions.mixed-to-improper-add-all": "That bug accepts improper fractions but converts to them wrongly; this belief rejects them."
}
} | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/4/NF/B/3/",
"label": "CCSS 4.NF.B.3: understand a fraction a/b with a > 1 as a sum of fractions 1/b"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/4/NF/B/3/",
"label": "CCSS ... | [
{
"scheme": "CCSS",
"code": "4.NF.B.3",
"uri": "http://corestandards.org/Math/Content/4/NF/B/3/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Stafylidou, S., & Vosniadou, S. (2004). The development of students' understanding of the numerical value of fractions. Learning and Instruction, 14(5), 503-518.",
"doi": "10.1016/j.learninstruc.2004.06.015",
"note": "A developmental stage in ... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.invert-both | https://open-misconceptions.github.io/miscon-data/m/math.fractions.invert-both | aa675277-3fb6-44fe-aad9-20dacc62d775 | 0.1.1 | draft | low | Inverting both fractions when dividing | To divide fractions you flip both fractions and then multiply. | procedural-bug | math.fractions | [
{
"scheme": "CCSS",
"code": "6.NS.A.1",
"uri": "http://corestandards.org/Math/Content/6/NS/A/1/"
}
] | [
"middle",
"secondary",
"adult"
] | en | [
{
"item_shape": "divide two proper fractions",
"signature": "inverts both dividend and divisor and multiplies",
"example": {
"item": "1/2 / 3/4 = ?",
"expected": "2/3",
"response": "8/3"
}
}
] | {
"vs_slip": "Consistent across items. A slip produces one inverted-both answer; the bug produces it every time and the learner can recite 'flip them and multiply'.",
"vs": {
"math.fractions.invert-dividend": "Invert-dividend gives 6/4 on 1/2 / 3/4; invert-both gives 8/3."
}
} | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/6/NS/A/1/",
"label": "CCSS 6.NS.A.1: interpret and compute quotients of fractions"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/6/NS/A/1/",
"label": "CCSS 6.NS.A.1: interpre... | [
{
"scheme": "CCSS",
"code": "6.NS.A.1",
"uri": "http://corestandards.org/Math/Content/6/NS/A/1/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Ashlock, R. B. (2010). Error Patterns in Computation: Using Error Patterns to Help Each Student Learn (10th ed.). Allyn & Bacon."
},
{
"type": "paper",
"citation": "Newton, K. J. (2008). An extensive analysis of preservice elementary te... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.invert-dividend | https://open-misconceptions.github.io/miscon-data/m/math.fractions.invert-dividend | 33e03294-fca9-4bef-92bc-386f55ec81de | 0.1.1 | draft | low | Inverting the first fraction when dividing | To divide fractions you flip the first fraction and then multiply. | procedural-bug | math.fractions | [
{
"scheme": "CCSS",
"code": "6.NS.A.1",
"uri": "http://corestandards.org/Math/Content/6/NS/A/1/"
}
] | [
"middle",
"secondary",
"adult"
] | en | [
{
"item_shape": "divide two proper fractions",
"signature": "inverts the dividend instead of the divisor and multiplies",
"example": {
"item": "1/2 / 3/4 = ?",
"expected": "2/3",
"response": "6/4 (= 3/2)"
}
}
] | {
"vs_slip": "Apply to several items. The bug inverts the first fraction every time; a slip flips the wrong one once and self-corrects when asked which fraction is the divisor.",
"vs": {
"math.fractions.invert-both": "Invert-both gives 2/1 x 4/3 = 8/3 on the same item; invert-dividend gives 2/1 x 3/4 = 6/4.",
... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/6/NS/A/1/",
"label": "CCSS 6.NS.A.1: interpret and compute quotients of fractions"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/6/NS/A/1/",
"label": "CCSS 6.NS.A.1: interpre... | [
{
"scheme": "CCSS",
"code": "6.NS.A.1",
"uri": "http://corestandards.org/Math/Content/6/NS/A/1/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Ashlock, R. B. (2010). Error Patterns in Computation: Using Error Patterns to Help Each Student Learn (10th ed.). Allyn & Bacon."
},
{
"type": "paper",
"citation": "Newton, K. J. (2008). An extensive analysis of preservice elementary te... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.mixed-to-improper-add-all | https://open-misconceptions.github.io/miscon-data/m/math.fractions.mixed-to-improper-add-all | be94771a-f7b8-4af6-acb3-a3fe723a0d20 | 0.1.1 | draft | low | Converting a mixed number by adding all its numbers | To write a mixed number as an improper fraction you add the whole number to the numerator and keep the denominator. | procedural-bug | math.fractions | [
{
"scheme": "CCSS",
"code": "4.NF.B.3",
"uri": "http://corestandards.org/Math/Content/4/NF/B/3/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "convert a mixed number to an improper fraction",
"signature": "numerator = whole + numerator; denominator unchanged",
"example": {
"item": "Write 2 1/3 as an improper fraction",
"expected": "7/3",
"response": "3/3"
}
}
] | {
"vs_slip": "Consistent across items. A slip is a wrong product within the multiply-then-add method.",
"vs": {
"math.fractions.add-whole-to-numerator": "Same surface result on 2 + 1/3, but this bug is triggered by mixed-number notation, not by a plus sign.",
"math.fractions.improper-impossible": "Improper-... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/4/NF/B/3/",
"label": "CCSS 4.NF.B.3: understand a fraction a/b with a > 1 as a sum of fractions 1/b"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/4/NF/B/3/",
"label": "CCSS ... | [
{
"scheme": "CCSS",
"code": "4.NF.B.3",
"uri": "http://corestandards.org/Math/Content/4/NF/B/3/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Ashlock, R. B. (2010). Error Patterns in Computation: Using Error Patterns to Help Each Student Learn (10th ed.). Allyn & Bacon."
},
{
"type": "book",
"citation": "Kerslake, D. (1986). Fractions: Children's Strategies and Errors. NFER-N... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.multiply-makes-bigger | https://open-misconceptions.github.io/miscon-data/m/math.fractions.multiply-makes-bigger | 04246969-9c77-41b0-a67b-b48be9b2f5a3 | 0.1.1 | draft | low | Multiplication always makes bigger | Multiplying always gives a result larger than the number you started with, so multiplying by a fraction cannot make a number smaller. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "5.NF.B.5",
"uri": "http://corestandards.org/Math/Content/5/NF/B/5/"
}
] | [
"primary",
"middle",
"secondary",
"adult"
] | en | [
{
"item_shape": "predict whether a product will be larger or smaller than a factor, without calculating",
"signature": "predicts the product of a number and a proper fraction is larger than the number",
"example": {
"item": "Without calculating, is 8 x 3/4 more or less than 8?",
"expected": ... | {
"vs_slip": "A slip is one wrong prediction. The belief is stated as a rule and generalises to decimals (0.5 x 8 'must be more than 8'); it often coexists with math.fractions.divide-makes-smaller.",
"vs": {
"math.fractions.divide-makes-smaller": "Mirror belief; test each separately with prediction items for mu... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/5/NF/B/5/",
"label": "CCSS 5.NF.B.5: interpret multiplication as scaling"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/5/NF/B/5/",
"label": "CCSS 5.NF.B.5: interpret multipl... | [
{
"scheme": "CCSS",
"code": "5.NF.B.5",
"uri": "http://corestandards.org/Math/Content/5/NF/B/5/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Fischbein, E., Deri, M., Nello, M. S., & Marino, M. S. (1985). The role of implicit models in solving verbal problems in multiplication and division. Journal for Research in Mathematics Education, 16(1), 3-17.",
"doi": "10.5951/jresematheduc.16.1.00... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.multiply-mixed-parts-separately | https://open-misconceptions.github.io/miscon-data/m/math.fractions.multiply-mixed-parts-separately | 89ca96fb-84d7-4b24-a0f0-c24cf282e25c | 0.1.1 | draft | low | Multiplying mixed numbers part by part | To multiply mixed numbers you multiply the whole numbers together and the fractions together and put the two results back together. | procedural-bug | math.fractions | [
{
"scheme": "CCSS",
"code": "5.NF.B.4",
"uri": "http://corestandards.org/Math/Content/5/NF/B/4/"
}
] | [
"middle"
] | en | [
{
"item_shape": "multiply two mixed numbers",
"signature": "product = (whole x whole) and (fraction x fraction) written as a mixed number; the cross terms are dropped",
"example": {
"item": "2 1/2 x 3 1/3 = ?",
"expected": "8 1/3",
"response": "6 1/6"
}
}
] | {
"vs_slip": "The answer is too small by exactly the two cross products and the pattern holds across items. A slip is an arithmetic error within the full method.",
"vs": {
"math.fractions.multiply-with-common-denominator": "That bug appears on proper-fraction items; this one only appears with mixed numbers."
... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/5/NF/B/4/",
"label": "CCSS 5.NF.B.4: multiply a fraction or whole number by a fraction"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/5/NF/B/4/",
"label": "CCSS 5.NF.B.4: mul... | [
{
"scheme": "CCSS",
"code": "5.NF.B.4",
"uri": "http://corestandards.org/Math/Content/5/NF/B/4/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Ashlock, R. B. (2010). Error Patterns in Computation: Using Error Patterns to Help Each Student Learn (10th ed.). Allyn & Bacon."
},
{
"type": "paper",
"citation": "Newton, K. J. (2008). An extensive analysis of preservice elementary te... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.multiply-with-common-denominator | https://open-misconceptions.github.io/miscon-data/m/math.fractions.multiply-with-common-denominator | 116cbd32-81bd-4fbb-b5b2-31a47ff576b4 | 0.1.1 | draft | low | Multiplying needs a common denominator | Before multiplying fractions you must write them with a common denominator, then multiply the numerators and keep the denominator. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "5.NF.B.4",
"uri": "http://corestandards.org/Math/Content/5/NF/B/4/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "multiply two fractions with unlike denominators",
"signature": "converts to a common denominator, multiplies numerators and keeps the common denominator",
"example": {
"item": "1/2 x 1/3 = ?",
"expected": "1/6",
"response": "3/6 x 2/6 = 6/6 = 1"
}
},
{
"ite... | {
"vs_slip": "The extra common-denominator step is visible in the working and repeated across items. A slip does not add that step.",
"vs": {
"math.fractions.cross-multiply-to-multiply": "Cross-multipliers do not convert denominators; they give 1/2 x 1/3 = (1x3)/(2x1) = 3/2.",
"math.fractions.add-across": "... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/5/NF/B/4/",
"label": "CCSS 5.NF.B.4: multiply a fraction or whole number by a fraction"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/5/NF/B/4/",
"label": "CCSS 5.NF.B.4: mul... | [
{
"scheme": "CCSS",
"code": "5.NF.B.4",
"uri": "http://corestandards.org/Math/Content/5/NF/B/4/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Newton, K. J. (2008). An extensive analysis of preservice elementary teachers' knowledge of fractions. American Educational Research Journal, 45(4), 1080-1110.",
"doi": "10.3102/0002831208320851",
"note": "Overgeneralisation of the addition pr... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.no-number-between | https://open-misconceptions.github.io/miscon-data/m/math.fractions.no-number-between | a18f0879-fc85-4c07-8da5-d1e68e72c460 | 0.1.1 | draft | low | No number between neighbouring fractions | Fractions come one after another like whole numbers, so between two fractions that are 'next to each other' there is no other number. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "6.NS.C.6",
"uri": "http://corestandards.org/Math/Content/6/NS/C/6/"
}
] | [
"middle",
"secondary"
] | en | [
{
"item_shape": "ask how many numbers lie between two fractions",
"signature": "answers none, or a small finite count found by listing",
"example": {
"item": "How many numbers are there between 1/5 and 2/5?",
"expected": "Infinitely many",
"response": "None"
}
},
{
"item_sh... | {
"vs_slip": "A slip is failing to find one on a single item. The belief is a stated rule ('there's nothing between them') that survives being shown an example, or is repaired to 'there are a few, but not infinitely many'."
} | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/6/NS/C/6/",
"label": "CCSS 6.NS.C.6: understand a rational number as a point on the number line"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/6/NS/C/6/",
"label": "CCSS 6.NS... | [
{
"scheme": "CCSS",
"code": "6.NS.C.6",
"uri": "http://corestandards.org/Math/Content/6/NS/C/6/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Vamvakoussi, X., & Vosniadou, S. (2004). Understanding the structure of the set of rational numbers: A conceptual change approach. Learning and Instruction, 14(5), 453-467.",
"doi": "10.1016/j.learninstruc.2004.06.013",
"note": "Discreteness o... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.number-line-whole-is-line | https://open-misconceptions.github.io/miscon-data/m/math.fractions.number-line-whole-is-line | fb647fd2-a6ef-40a4-a0ac-abd0d497e750 | 0.1.1 | draft | low | The whole line is the whole | On a number line the fraction refers to the whole line drawn, so 1/2 is at the middle of the line wherever the line ends. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "3.NF.A.2",
"uri": "http://corestandards.org/Math/Content/3/NF/A/2/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "place a fraction on a number line longer than one unit",
"signature": "places the fraction at that fraction of the whole drawn segment rather than of the unit interval",
"example": {
"item": "Mark 1/2 on a number line from 0 to 3",
"expected": "halfway between 0 and 1",
... | {
"vs_slip": "Correct on 0-to-1 lines and wrong on longer lines, consistently. A slip has no such dependence on line length.",
"vs": {
"math.fractions.two-whole-numbers": "Learners who see a fraction as two whole numbers fail 0-to-1 lines too, placing 3/4 at 3 or 4."
}
} | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/3/NF/A/2/",
"label": "CCSS 3.NF.A.2: understand a fraction as a number on the number line"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/3/NF/A/2/",
"label": "CCSS 3.NF.A.2: ... | [
{
"scheme": "CCSS",
"code": "3.NF.A.2",
"uri": "http://corestandards.org/Math/Content/3/NF/A/2/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Bright, G. W., Behr, M. J., Post, T. R., & Wachsmuth, I. (1988). Identifying fractions on number lines. Journal for Research in Mathematics Education, 19(3), 215-232.",
"doi": "10.5951/jresematheduc.19.3.0215",
"note": "Number-line tasks: stud... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.of-quantity-swap-roles | https://open-misconceptions.github.io/miscon-data/m/math.fractions.of-quantity-swap-roles | 721c3f30-4b4e-4ffb-ac77-3433d1a18164 | 0.1.1 | draft | low | Swapping numerator and denominator when finding a fraction of a quantity | To find a/b of a quantity you divide the quantity by a and multiply by b. | procedural-bug | math.fractions | [
{
"scheme": "CCSS",
"code": "4.NF.B.4",
"uri": "http://corestandards.org/Math/Content/4/NF/B/4/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "find a non-unit fraction of a whole-number quantity",
"signature": "divides by the numerator and multiplies by the denominator",
"example": {
"item": "Find 3/4 of 20",
"expected": "15",
"response": "26 2/3 (20 / 3 x 4)"
}
},
{
"item_shape": "find a unit fra... | {
"vs_slip": "The answer is larger than the original quantity for a proper fraction and the learner does not object. A slip is a wrong division or multiplication within the right method."
} | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/4/NF/B/4/",
"label": "CCSS 4.NF.B.4: multiply a fraction by a whole number"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/4/NF/B/4/",
"label": "CCSS 4.NF.B.4: multiply a frac... | [
{
"scheme": "CCSS",
"code": "4.NF.B.4",
"uri": "http://corestandards.org/Math/Content/4/NF/B/4/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Hart, K. M. (Ed.). (1981). Children's Understanding of Mathematics: 11-16. John Murray. (Concepts in Secondary Mathematics and Science project.)",
"note": "CSMS fractions: errors on 'fraction of a quantity' items."
},
{
"type": "book",
... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.part-to-part | https://open-misconceptions.github.io/miscon-data/m/math.fractions.part-to-part | 15a57c88-bbde-47b3-bd0d-6771a62e6cec | 0.1.1 | draft | low | Writing the shaded part over the unshaded part | A fraction compares the shaded part with the unshaded part, so the number of shaded pieces goes on top and the number of unshaded pieces goes underneath. | notation-confusion | math.fractions | [
{
"scheme": "CCSS",
"code": "3.NF.A.1",
"uri": "http://corestandards.org/Math/Content/3/NF/A/1/"
}
] | [
"early-primary",
"primary"
] | en | [
{
"item_shape": "name the fraction shaded in a shape divided into equal parts",
"signature": "writes shaded/unshaded instead of shaded/total",
"example": {
"item": "A bar is cut into 5 equal parts and 3 are shaded. What fraction is shaded?",
"expected": "3/5",
"response": "3/2"
}
... | {
"vs_slip": "Consistent across items, and the learner produces 'fractions' larger than one for a majority-shaded shape without noticing. A slip is one miswritten denominator.",
"vs": {
"math.fractions.unequal-parts": "Unequal-parts believers write the correct denominator (the total count) on equal-parts shapes... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/3/NF/A/1/",
"label": "CCSS 3.NF.A.1: understand a fraction 1/b as one part of a whole partitioned into b equal parts"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/3/NF/A/1/",
... | [
{
"scheme": "CCSS",
"code": "3.NF.A.1",
"uri": "http://corestandards.org/Math/Content/3/NF/A/1/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Hart, K. M. (Ed.). (1981). Children's Understanding of Mathematics: 11-16. John Murray. (Concepts in Secondary Mathematics and Science project.)",
"note": "CSMS fractions items: part-part responses on shaded-region tasks."
},
{
"type": ... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.subtract-across | https://open-misconceptions.github.io/miscon-data/m/math.fractions.subtract-across | f9b8d0fd-1f46-47ac-8fc7-d4923e7ef2c8 | 0.1.1 | draft | low | Subtracting fractions across numerators and denominators | Fractions are subtracted by subtracting the numerators and subtracting the denominators. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "5.NF.A.1",
"uri": "http://corestandards.org/Math/Content/5/NF/A/1/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "subtract two fractions with unlike denominators",
"signature": "difference numerator = a - c and difference denominator = b - d for a/b - c/d",
"example": {
"item": "3/4 - 1/2 = ?",
"expected": "1/4",
"response": "2/2 (= 1)"
}
},
{
"item_shape": "subtract t... | {
"vs_slip": "Like-denominator items are diagnostic: the bug produces a zero denominator and the learner stalls. A slip does not.",
"vs": {
"math.fractions.add-across": "Same mechanism for the other operation. Most learners with one have the other; test both."
}
} | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/5/NF/A/1/",
"label": "CCSS 5.NF.A.1: add and subtract fractions with unlike denominators"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/5/NF/A/1/",
"label": "CCSS 5.NF.A.1: a... | [
{
"scheme": "CCSS",
"code": "5.NF.A.1",
"uri": "http://corestandards.org/Math/Content/5/NF/A/1/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Siegler, R. S., Thompson, C. A., & Schneider, M. (2011). An integrated theory of whole number and fractions development. Cognitive Psychology, 62(4), 273-296.",
"doi": "10.1016/j.cogpsych.2011.03.001"
},
{
"type": "paper",
"citat... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.two-whole-numbers | https://open-misconceptions.github.io/miscon-data/m/math.fractions.two-whole-numbers | dd52364b-0b0d-4ab8-a0f5-51bcb845f7fc | 0.1.1 | draft | low | A fraction is two separate whole numbers | A fraction is two whole numbers written one above the other, not a single number with its own size; the numerator and denominator can be read and handled separately. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "3.NF.A.2",
"uri": "http://corestandards.org/Math/Content/3/NF/A/2/"
},
{
"scheme": "CCSS",
"code": "6.NS.C.6",
"uri": "http://corestandards.org/Math/Content/6/NS/C/6/"
}
] | [
"primary",
"middle"
] | en | [
{
"item_shape": "place a fraction on a number line marked 0 to 10",
"signature": "places the fraction at the numerator, the denominator, or their sum",
"example": {
"item": "Mark 3/4 on a number line from 0 to 10",
"expected": "between 0 and 1, three quarters of the way",
"response": "... | {
"vs_slip": "A slip is one misplaced point. The belief is stable across fractions and shows in language: the learner describes 3/4 as 'three and four' or 'three out of four' but cannot say whether it is more or less than one.",
"vs": {
"math.fractions.number-line-whole-is-line": "Give a 0-to-1 line. Learners w... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/3/NF/A/2/",
"label": "CCSS 3.NF.A.2: understand a fraction as a number on the number line"
},
{
"external": "http://corestandards.org/Math/Content/6/NS/C/6/",
"label": "CCSS 6.NS.C.6: understand a rational n... | [
{
"scheme": "CCSS",
"code": "3.NF.A.2",
"uri": "http://corestandards.org/Math/Content/3/NF/A/2/",
"relation": "about"
}
] | {
"sources": [
{
"type": "paper",
"citation": "Ni, Y., & Zhou, Y.-D. (2005). Teaching and learning fraction and rational numbers: The origins and implications of whole number bias. Educational Psychologist, 40(1), 27-52.",
"doi": "10.1207/s15326985ep4001_3",
"note": "Whole number bias: the... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
math.fractions.unequal-parts | https://open-misconceptions.github.io/miscon-data/m/math.fractions.unequal-parts | e7a0875c-e339-4404-9f39-1f73cfe9206f | 0.1.2 | draft | low | Any part of a shape cut into b pieces is 1/b | If a shape is cut into b pieces, each piece is one b-th of the shape, whether or not the pieces are the same size. | overgeneralization | math.fractions | [
{
"scheme": "CCSS",
"code": "3.NF.A.1",
"uri": "http://corestandards.org/Math/Content/3/NF/A/1/"
}
] | [
"early-primary",
"primary"
] | en | [
{
"item_shape": "name the fraction shaded in a shape divided into unequal parts",
"signature": "counts pieces and writes shaded/total, ignoring the sizes of the pieces",
"example": {
"item": "A rectangle is cut into 4 pieces of different sizes; the largest is shaded. What fraction is shaded?",
... | {
"vs_slip": "Ask directly whether the pieces need to be the same size. A slip is a miscount with equal parts assumed; the belief is a stated 'it doesn't matter, there are four pieces'.",
"vs": {
"math.fractions.part-to-part": "Use a shape with equal parts. Part-to-part writers give 3/2 for 3 shaded of 5; this ... | {
"conflicts_with": [
{
"external": "http://corestandards.org/Math/Content/3/NF/A/1/",
"label": "CCSS 3.NF.A.1: understand a fraction 1/b as one part of a whole partitioned into b equal parts"
}
],
"resolved_by": [
{
"external": "http://corestandards.org/Math/Content/3/NF/A/1/",
... | [
{
"scheme": "CCSS",
"code": "3.NF.A.1",
"uri": "http://corestandards.org/Math/Content/3/NF/A/1/",
"relation": "about"
}
] | {
"sources": [
{
"type": "book",
"citation": "Kerslake, D. (1986). Fractions: Children's Strategies and Errors. NFER-Nelson."
},
{
"type": "book",
"citation": "Steffe, L. P., & Olive, J. (2010). Children's Fractional Knowledge. Springer.",
"doi": "10.1007/978-1-4419-0591-8",
... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.arrays.arrays-grow | https://open-misconceptions.github.io/miscon-data/m/programming.arrays.arrays-grow | c14aea0d-dc29-4cdc-9e08-bde06dfa0014 | 0.1.1 | draft | low | Arrays grow when you add to them | An array gets bigger by itself when you store something past its end, so its size does not need to be decided in advance. | overgeneralization | programming.arrays | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.arrays.fixed-size"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "predict a write one past the end of an array",
"signature": "predicts the array now has one more element",
"example": {
"item": "int[] a = new int[3];\na[3] = 7;\nSystem.out.println(a.length);",
"expected": "ArrayIndexOutOfBoundsException",
"response": "4"
}
}
] | {
"vs_slip": "Consistent across items; the learner treats arrays like lists. A slip is a single off-by-one index."
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.arrays.fixed-size",
"label": "An array has a fixed length set when it is created"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.... | [
{
"scheme": "progmiscon",
"code": "Java/ArraysGrow",
"uri": "https://progmiscon.org/misconceptions/Java/ArraysGrow",
"relation": "close-match"
},
{
"scheme": "progmiscon",
"code": "Java/ArrayListIsArray",
"uri": "https://progmiscon.org/misconceptions/Java/ArrayListIsArray",
"rela... | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.arrays.length-is-a-method | https://open-misconceptions.github.io/miscon-data/m/programming.arrays.length-is-a-method | 38f22ed3-8b31-4032-9be3-581599629ee5 | 0.1.1 | draft | low | An array's length is a method call | You get the length of an array by calling a method on it, in the same way as for a string or a list. | notation-confusion | programming.arrays | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.arrays.length"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "write the length of an array",
"signature": "writes length() or size() on an array",
"example": {
"item": "Given int[] a, write an expression for its length.",
"expected": "a.length",
"response": "a.length() (or a.size())"
}
}
] | {
"vs_slip": "A slip is a typo fixed on the first compile error. The belief persists across items and the learner explains that 'everything is a method'."
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.arrays.length",
"label": "An array's length is a property, not a method"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.arrays.le... | [
{
"scheme": "progmiscon",
"code": "Java/ArrayHasLengthMethod",
"uri": "https://progmiscon.org/misconceptions/Java/ArrayHasLengthMethod",
"relation": "close-match"
}
] | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.booleans.must-compare-with-literal | https://open-misconceptions.github.io/miscon-data/m/programming.booleans.must-compare-with-literal | 1e4090f5-0d1e-4bf3-af12-7671e11aaf09 | 0.1.1 | draft | low | A boolean must be compared with true to be used as a condition | A boolean variable or expression cannot be used directly as a condition; it has to be compared with true or false first, and a comparison is the only thing that produces a condition. | undergeneralization | programming.boolean | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.booleans.expression"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "write a condition from a boolean variable",
"signature": "writes == true (or == True) and cannot explain what if done: alone would do",
"example": {
"item": "done is a boolean. Write the condition for 'if done'.",
"expected": "if done:",
"response": "if done == True:"
... | {
"vs_slip": "A slip is a stylistic habit the learner can drop when asked. The belief is the claim that if done: is invalid or that a comparison is not a value."
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.booleans.expression",
"label": "A boolean expression is itself a value"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.booleans.e... | [
{
"scheme": "progmiscon",
"code": "Java/ComparisonWithBooleanLiteral",
"uri": "https://progmiscon.org/misconceptions/Java/ComparisonWithBooleanLiteral",
"relation": "close-match"
},
{
"scheme": "progmiscon",
"code": "Python/ComparisonWithBoolLiteral",
"uri": "https://progmiscon.org/m... | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.booleans.no-short-circuit | https://open-misconceptions.github.io/miscon-data/m/programming.booleans.no-short-circuit | 835a754e-f33f-4ab3-88a1-2cc87dc58918 | 0.1.1 | draft | low | Both operands of and/or are always evaluated | A logical and or or always evaluates both of its operands, whatever the first one turns out to be. | undergeneralization | programming.boolean | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.booleans.short-circuit"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "predict whether a guarded expression raises an error",
"signature": "predicts an error from the second operand even though the first operand decides the result",
"example": {
"item": "items = []\nif len(items) > 0 and items[0] == 'x':\n print('yes')\nelse:\n print('no')",
... | {
"vs_slip": "Consistent across items; the learner can state 'it checks both'. A slip is a single wrong prediction."
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.booleans.short-circuit",
"label": "Logical and/or stop evaluating once the result is known"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/pr... | [
{
"scheme": "progmiscon",
"code": "Java/NoShortCircuit",
"uri": "https://progmiscon.org/misconceptions/Java/NoShortCircuit",
"relation": "close-match"
},
{
"scheme": "progmiscon",
"code": "Python/NoShortCircuit",
"uri": "https://progmiscon.org/misconceptions/Python/NoShortCircuit",
... | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.control.conditional-is-sequence | https://open-misconceptions.github.io/miscon-data/m/programming.control.conditional-is-sequence | 7e5b6c85-5df3-4013-8746-0f18576e8b5a | 0.1.1 | draft | low | Both branches of an if-else run in turn | In an if-else statement the if branch runs when the condition is true and then the else branch runs afterwards as well, because it comes next in the code. | overgeneralization | programming.control | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.control.conditional"
}
] | [
"primary",
"middle",
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "trace an if-else where the condition is true",
"signature": "reports the effects of both branches",
"example": {
"item": "x = 5\nif x > 0:\n print('positive')\nelse:\n print('not positive')",
"expected": "positive",
"response": "positive\nnot positive"
}
}
... | {
"vs_slip": "Consistent across items and the learner explains 'it does this one and then that one'. A slip is a single wrong branch.",
"vs": {
"programming.control.if-is-loop": "If-loopers repeat one branch; sequence believers run both once."
}
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.control.conditional",
"label": "An if statement evaluates its condition once and runs at most one branch"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/mi... | [
{
"scheme": "progmiscon",
"code": "Java/ConditionalIsSequence",
"uri": "https://progmiscon.org/misconceptions/Java/ConditionalIsSequence",
"relation": "close-match"
},
{
"scheme": "progmiscon",
"code": "Scratch/ConditionalIsSequence",
"uri": "https://progmiscon.org/misconceptions/Scr... | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.control.if-is-loop | https://open-misconceptions.github.io/miscon-data/m/programming.control.if-is-loop | aa78ad26-c8b4-4d72-8e2f-84a48c0efed1 | 0.1.1 | draft | low | An if statement repeats while its condition holds | The body of an if statement keeps running for as long as the condition is true, like a while loop. | misapplied-analogy | programming.control | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.control.conditional"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "trace an if statement whose body keeps its condition true",
"signature": "predicts repeated execution of the body",
"example": {
"item": "x = 0\nif x < 3:\n x = x + 1\nprint(x)",
"expected": "1",
"response": "3"
}
}
] | {
"vs_slip": "Consistent across items; the learner describes the if as 'checking until'. A slip is a single wrong count.",
"vs": {
"programming.control.while-checked-continuously": "That belief is about while loops exiting mid-body; this one is about if statements looping.",
"programming.control.conditional... | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.control.conditional",
"label": "An if statement evaluates its condition once and runs at most one branch"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/mi... | [
{
"scheme": "progmiscon",
"code": "Java/IfIsLoop",
"uri": "https://progmiscon.org/misconceptions/Java/IfIsLoop",
"relation": "close-match"
}
] | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.control.loop-body-variables-reset | https://open-misconceptions.github.io/miscon-data/m/programming.control.loop-body-variables-reset | 300e50db-d430-4eaa-928f-d34e302f6c48 | 0.1.1 | draft | low | Variables reset at the start of every loop iteration | Every time a loop body starts again, the variables changed inside it go back to what they were before the loop. | overgeneralization | programming.control | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.control.loop"
},
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.variables.variable"
}
] | [
"primary",
"middle",
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "trace an accumulator updated inside a loop",
"signature": "reports the value from a single iteration rather than the accumulated value",
"example": {
"item": "total = 0\nfor n in [1, 2, 3]:\n total = total + n\nprint(total)",
"expected": "6",
"response": "3"
}
... | {
"vs_slip": "Consistent across accumulator items; the learner explains that the loop 'starts over'. A slip is an arithmetic error in the running total.",
"vs": {
"programming.variables.variable-keeps-history": "History-keepers report too many values; resetters report only the last iteration's contribution."
... | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.variables.variable",
"label": "A variable holds exactly one value at a time"
},
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.control.loop",
"label"... | [
{
"scheme": "progmiscon",
"code": "Scratch/ResetStateEachLoopIteration",
"uri": "https://progmiscon.org/misconceptions/Scratch/ResetStateEachLoopIteration",
"relation": "close-match"
}
] | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.control.while-checked-continuously | https://open-misconceptions.github.io/miscon-data/m/programming.control.while-checked-continuously | 8ed015e5-884f-4e76-91d6-2d5f339b2392 | 0.1.1 | draft | low | A while loop stops the instant its condition becomes false | The condition of a while loop is watched continuously, so the loop exits in the middle of the body the moment the condition turns false. | misapplied-analogy | programming.control | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.control.loop"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "trace a while loop whose condition becomes false partway through the body",
"signature": "stops the trace before the rest of the body runs on the final iteration",
"example": {
"item": "i = 0\nwhile i < 2:\n i = i + 1\n print(i)",
"expected": "1\n2",
"response": ... | {
"vs_slip": "Consistent across items, especially when the update comes before other statements in the body. A slip is a single dropped line.",
"vs": {
"programming.control.if-is-loop": "Different statement; test each with its own item."
}
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.control.loop",
"label": "A loop checks its condition only at defined points and repeats its whole body"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/misc... | null | {
"sources": [
{
"type": "paper",
"citation": "Pea, R. D. (1986). Language-independent conceptual \"bugs\" in novice programming. Journal of Educational Computing Research, 2(1), 25-36.",
"doi": "10.2190/689T-1R2A-X4W4-29J2",
"note": "Parallelism bug: several lines believed to be active at... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.execution.all-statements-active | https://open-misconceptions.github.io/miscon-data/m/programming.execution.all-statements-active | a3989f3c-0cf8-4317-874b-f9b8fd9c12e2 | 0.1.1 | draft | low | All the statements in a program are active at once | Every line of a program is active at the same time, so a later line can affect what an earlier line did, and a condition anywhere is watched continuously. | misapplied-analogy | programming.execution | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.execution.sequential-execution"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "trace a program where a later assignment would matter if it applied retroactively",
"signature": "applies the later value to the earlier output",
"example": {
"item": "x = 1\nprint(x)\nx = 2",
"expected": "1",
"response": "2"
}
}
] | {
"vs_slip": "Consistent across items; the learner talks about the program 'as a whole' rather than step by step. A slip is a single wrong step.",
"vs": {
"programming.control.while-checked-continuously": "The while case is a special case of this belief; a learner may show it only for loop conditions."
}
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.execution.sequential-execution",
"label": "Statements run one at a time in order"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.... | null | {
"sources": [
{
"type": "paper",
"citation": "Pea, R. D. (1986). Language-independent conceptual \"bugs\" in novice programming. Journal of Educational Computing Research, 2(1), 25-36.",
"doi": "10.2190/689T-1R2A-X4W4-29J2",
"note": "Parallelism bug."
},
{
"type": "book",
... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.execution.computer-infers-intent | https://open-misconceptions.github.io/miscon-data/m/programming.execution.computer-infers-intent | 0b67ef75-97f2-4e35-8de8-058b5a78261b | 0.1.1 | draft | low | The computer fills in what you meant | The computer understands the purpose of the program and fills in steps that were left out, so a program does what you meant as long as the intention is clear. | misapplied-analogy | programming.execution | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.execution.literal-interpretation"
}
] | [
"primary",
"middle",
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "predict the output of a program with a missing step",
"signature": "predicts the intended output rather than the literal one",
"example": {
"item": "numbers = [3, 1, 2]\nprint(numbers) # print sorted",
"expected": "[3, 1, 2]",
"response": "[1, 2, 3]"
}
}
] | {
"vs_slip": "Consistent across items and the learner appeals to what the program is 'for'. A slip is a single misread.",
"vs": {
"programming.variables.names-meaningful-to-machine": "The variable-name case is a special case; test with an item where the intention is stated only in a comment."
}
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.execution.literal-interpretation",
"label": "The machine does exactly what the code says"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/prog... | null | {
"sources": [
{
"type": "paper",
"citation": "Pea, R. D. (1986). Language-independent conceptual \"bugs\" in novice programming. Journal of Educational Computing Research, 2(1), 25-36.",
"doi": "10.2190/689T-1R2A-X4W4-29J2",
"note": "Intentionality and egocentrism bugs."
},
{
... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.functions.argument-name-must-match-parameter | https://open-misconceptions.github.io/miscon-data/m/programming.functions.argument-name-must-match-parameter | e7df53b7-374a-4b33-86e9-3c2883c5374f | 0.1.1 | draft | low | Arguments are matched to parameters by name | The variable passed to a function has to have the same name as the parameter, or the function will not receive it. | misapplied-analogy | programming.functions | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.functions.parameter-passing"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "predict the output of a call whose argument name differs from the parameter name",
"signature": "predicts an error or that the parameter is unset",
"example": {
"item": "def show(n):\n print(n)\nvalue = 5\nshow(value)",
"expected": "5",
"response": "Error: n is not ... | {
"vs_slip": "Consistent renaming or predicted errors across items. A slip is a single wrong name.",
"vs": {
"programming.functions.parameters-alias-arguments": "Aliasers accept different names but expect changes to the parameter to flow back; name-matchers do not accept different names at all."
}
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.functions.parameter-passing",
"label": "Arguments are matched to parameters by position and copied in"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/misco... | null | {
"sources": [
{
"type": "paper",
"citation": "Fleury, A. E. (1991). Parameter passing: The rules the students construct. In Proceedings of the 22nd SIGCSE Technical Symposium on Computer Science Education (SIGCSE '91), 283-286.",
"doi": "10.1145/107004.107066",
"note": "Student-constructe... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.functions.base-case-not-needed | https://open-misconceptions.github.io/miscon-data/m/programming.functions.base-case-not-needed | 09dac977-0121-45e8-8a5c-0aa059faf59c | 0.1.2 | draft | low | A recursive function stops by itself | A recursive function stops calling itself when there is nothing left to do, so it does not need an explicit base case. | misapplied-analogy | programming.functions | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.functions.base-case"
}
] | [
"middle",
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "predict the behaviour of a recursive function with no base case",
"signature": "predicts termination with a sensible answer",
"example": {
"item": "def count_down(n):\n print(n)\n count_down(n - 1)\ncount_down(3)",
"expected": "3 2 1 0 -1 ... until the recursion limit ... | {
"vs_slip": "A slip is one forgotten base case the learner adds when asked how it stops. The belief is the answer 'it stops when n runs out'.",
"vs": {
"programming.functions.recursion-as-loop": "Loop-model holders often include a base case but expect only one copy of the variables; base-case omitters expect t... | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.functions.base-case",
"label": "A recursive function stops only when a base case returns"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/prog... | [
{
"scheme": "progmiscon",
"code": "Scratch/BaseCaseNotNeeded",
"uri": "https://progmiscon.org/misconceptions/Scratch/BaseCaseNotNeeded",
"relation": "close-match"
}
] | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.functions.multiple-return-values | https://open-misconceptions.github.io/miscon-data/m/programming.functions.multiple-return-values | ba72c8c8-9a30-4f6a-9c9f-50370cde1a2f | 0.1.1 | draft | low | A function can return several separate values | return a, b sends back two separate values, so the caller receives two things rather than one tuple. | undergeneralization | programming.functions | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.functions.single-return-value"
}
] | [
"undergraduate"
] | en | [
{
"item_shape": "predict the type of a call that returns a comma-separated list",
"signature": "predicts two values, or that the second is lost, rather than one tuple",
"example": {
"item": "def f():\n return 1, 2\nx = f()\nprint(type(x))",
"expected": "<class 'tuple'>",
"response":... | {
"vs_slip": "Consistent across items and revealed by asking what x holds after x = f(). A slip is a single wrong type."
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.functions.single-return-value",
"label": "A function returns one value; several values travel as one tuple"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/... | [
{
"scheme": "progmiscon",
"code": "Python/MultipleValuesReturn",
"uri": "https://progmiscon.org/misconceptions/Python/MultipleValuesReturn",
"relation": "close-match"
}
] | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.functions.parameters-alias-arguments | https://open-misconceptions.github.io/miscon-data/m/programming.functions.parameters-alias-arguments | 7e500e88-daa7-49cb-a8f4-d0e0d6a62db0 | 0.1.1 | draft | low | Changing a parameter changes the caller's variable | A parameter is the same variable as the argument that was passed in, so assigning to the parameter inside the function changes the caller's variable, even for numbers and strings. | overgeneralization | programming.functions | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.functions.parameter-passing"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "trace a function that reassigns a primitive parameter",
"signature": "reports the caller's variable as changed",
"example": {
"item": "def bump(n):\n n = n + 1\nx = 1\nbump(x)\nprint(x)",
"expected": "1",
"response": "2"
}
}
] | {
"vs_slip": "Consistent across items with primitive arguments. A slip is a single wrong trace.",
"vs": {
"programming.functions.argument-name-must-match-parameter": "Name-matchers predict errors when names differ; aliasers accept different names.",
"programming.objects.assignment-copies-object": "The mirro... | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.functions.parameter-passing",
"label": "Arguments are matched to parameters by position and copied in"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/misco... | null | {
"sources": [
{
"type": "paper",
"citation": "Fleury, A. E. (1991). Parameter passing: The rules the students construct. In Proceedings of the 22nd SIGCSE Technical Symposium on Computer Science Education (SIGCSE '91), 283-286.",
"doi": "10.1145/107004.107066"
},
{
"type": "paper"... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.functions.print-is-return | https://open-misconceptions.github.io/miscon-data/m/programming.functions.print-is-return | c75e0b4a-c9c4-41af-af83-a095635ace63 | 0.1.1 | draft | low | Printing a value is the same as returning it | A function gives its result back by printing it, so a function that prints its answer can be used in an expression, and return is just another way to display. | misapplied-analogy | programming.functions | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.functions.return"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "use the result of a function that prints instead of returning",
"signature": "expects the printed value to be available to the caller",
"example": {
"item": "def double(n):\n print(n * 2)\nx = double(4)\nprint(x + 1)",
"expected": "8 then TypeError (x is None)",
"re... | {
"vs_slip": "A slip is one missing return the learner spots on rereading. The belief is a stated equivalence ('print gives it back') and persists after seeing None."
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.functions.return",
"label": "return hands a value back to the caller and ends the call"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/progra... | null | {
"sources": [
{
"type": "book",
"citation": "Sorva, J. (2012). Visual Program Simulation in Introductory Programming Education (Doctoral dissertation, Aalto University). Appendix A catalogues introductory programming misconceptions from the literature.",
"url": "https://aaltodoc.aalto.fi/handle... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.functions.recursion-as-loop | https://open-misconceptions.github.io/miscon-data/m/programming.functions.recursion-as-loop | fee3c932-6d7c-4816-aab9-c1dfe916ef15 | 0.1.1 | draft | low | A recursive call jumps back to the start | A recursive call is a jump back to the beginning of the function, using the same variables, so there is only ever one copy of the function running. | misapplied-analogy | programming.functions | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.functions.recursion"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "trace a recursive function that does work after the recursive call",
"signature": "omits or misorders the work done after each call returns",
"example": {
"item": "def show(n):\n if n == 0:\n return\n show(n - 1)\n print(n)\nshow(3)",
"expected": "1\n2\n3",
... | {
"vs_slip": "Consistent across items with post-call work; the learner draws a single frame. A slip is a single ordering error.",
"vs": {
"programming.functions.base-case-not-needed": "Base-case omitters are diagnosed by termination questions; loop-model holders by post-call ordering."
}
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.functions.recursion",
"label": "Each recursive call has its own activation with its own variables"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-da... | null | {
"sources": [
{
"type": "paper",
"citation": "Kahney, H. (1983). What do novice programmers know about recursion? In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (CHI '83), 235-239.",
"doi": "10.1145/800045.801618",
"note": "The 'looping' model of recursion."... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.objects.assignment-copies-object | https://open-misconceptions.github.io/miscon-data/m/programming.objects.assignment-copies-object | bf369c82-773c-4072-950c-55b6d9464684 | 0.1.1 | draft | low | Assigning an object makes a copy | Assigning one object variable to another makes a second, independent copy of the object, so changing one does not affect the other. | overgeneralization | programming.objects | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.objects.reference"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "trace a mutation through an aliased object",
"signature": "reports the other variable's object as unchanged",
"example": {
"item": "a = [1, 2]\nb = a\nb.append(3)\nprint(a)",
"expected": "[1, 2, 3]",
"response": "[1, 2]"
}
}
] | {
"vs_slip": "Consistent across items with mutable objects, and the learner is surprised by the result. A slip is a single wrong trace.",
"vs": {
"programming.objects.variables-hold-objects": "Same observable error; variables-hold-objects is the underlying model (the variable is the object). Ask the learner to ... | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.objects.reference",
"label": "An object variable holds a reference; assignment copies the reference"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-... | [
{
"scheme": "progmiscon",
"code": "Java/AssignmentCopiesObject",
"uri": "https://progmiscon.org/misconceptions/Java/AssignmentCopiesObject",
"relation": "close-match"
},
{
"scheme": "progmiscon",
"code": "Python/AssignmentCopiesObject",
"uri": "https://progmiscon.org/misconceptions/P... | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.objects.constant-reference-is-immutable | https://open-misconceptions.github.io/miscon-data/m/programming.objects.constant-reference-is-immutable | 371c613b-da3c-49d9-917e-3758758a1a81 | 0.1.1 | draft | low | A constant reference means an unchangeable object | Declaring an object variable final or const makes the object it refers to unchangeable, so its fields or elements cannot be modified. | overgeneralization | programming.objects | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.objects.immutability"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "predict a mutation through a final/const reference",
"signature": "predicts an error",
"example": {
"item": "const items = [1, 2];\nitems.push(3);\nconsole.log(items);",
"expected": "[1, 2, 3]",
"response": "TypeError (or 'not allowed')"
}
}
] | {
"vs_slip": "Consistent across items and the learner says const 'freezes' the value. A slip is a single wrong prediction."
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.objects.immutability",
"label": "A constant reference does not make the referenced object immutable"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-... | [
{
"scheme": "progmiscon",
"code": "Java/FinalReferenceImpliesImmutability",
"uri": "https://progmiscon.org/misconceptions/Java/FinalReferenceImpliesImmutability",
"relation": "close-match"
},
{
"scheme": "progmiscon",
"code": "JavaScript/ConstReferenceImpliesImmutability",
"uri": "ht... | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.objects.constructor-returns-object | https://open-misconceptions.github.io/miscon-data/m/programming.objects.constructor-returns-object | 82998d6e-dc24-425a-984e-e60d6a3b1de6 | 0.1.1 | draft | low | A constructor must return the object | A constructor creates the object and has to return it at the end, so a constructor without a return statement produces nothing. | overgeneralization | programming.objects | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.objects.constructor"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "write a constructor",
"signature": "adds return this (or return self) at the end, or a return type to the constructor header",
"example": {
"item": "Write a constructor for Point that stores x and y.",
"expected": "Point(int x, int y) { this.x = x; this.y = y; }",
"res... | {
"vs_slip": "A slip is a stray return removed when noticed. The belief is stated ('otherwise you don't get the object back') and the learner also expects new Point(1, 2) to be 'empty' without it."
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.objects.constructor",
"label": "A constructor initialises an object the runtime has already created"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-... | [
{
"scheme": "progmiscon",
"code": "Java/ConstructorReturnsObject",
"uri": "https://progmiscon.org/misconceptions/Java/ConstructorReturnsObject",
"relation": "close-match"
},
{
"scheme": "progmiscon",
"code": "Python/InitReturnsObject",
"uri": "https://progmiscon.org/misconceptions/Py... | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.objects.equality-compares-contents | https://open-misconceptions.github.io/miscon-data/m/programming.objects.equality-compares-contents | 23722159-9645-4246-a122-1d6ea3fd6ddf | 0.1.1 | draft | low | == compares the contents of objects | Comparing two object variables with == compares what is inside the objects, so two objects with the same field values are equal. | overgeneralization | programming.objects | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.objects.identity-vs-equality"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "predict == on two distinct objects with equal contents",
"signature": "predicts true",
"example": {
"item": "String a = new String(\"hi\");\nString b = new String(\"hi\");\nSystem.out.println(a == b);",
"expected": "false",
"response": "true"
}
}
] | {
"vs_slip": "Consistent across items and the learner sees no difference between == and equals. A slip is choosing the wrong operator once while knowing the difference.",
"vs": {
"programming.objects.variables-hold-objects": "Learners with no reference concept also predict true, but for a different reason (they... | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.objects.identity-vs-equality",
"label": "== on references compares identity, not contents"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/pro... | [
{
"scheme": "progmiscon",
"code": "Java/EqualityOperatorComparesObjectsValues",
"uri": "https://progmiscon.org/misconceptions/Java/EqualityOperatorComparesObjectsValues",
"relation": "close-match"
}
] | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.objects.variables-hold-objects | https://open-misconceptions.github.io/miscon-data/m/programming.objects.variables-hold-objects | d4a1fd15-44b9-4752-b086-b9a07a1e7ae7 | 0.1.1 | draft | low | A variable contains the whole object | An object variable contains the object itself, not a reference to it, so every variable is its own object and passing it around passes the object. | misapplied-analogy | programming.objects | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.objects.reference"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "draw or describe memory after two variables refer to one object",
"signature": "draws two separate objects, one inside each variable",
"example": {
"item": "p = Point(1, 2)\nq = p\nDraw p and q.",
"expected": "Two variables, both pointing to one Point object",
"respons... | {
"vs_slip": "Diagnosed by the drawing or by identity questions; the model is consistent. A slip is a single wrong prediction with a correct drawing.",
"vs": {
"programming.objects.assignment-copies-object": "Assignment-copies is the behavioural prediction; this record is the memory model behind it. Use the dra... | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.objects.reference",
"label": "An object variable holds a reference; assignment copies the reference"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-... | [
{
"scheme": "progmiscon",
"code": "Python/VariablesHoldObjects",
"uri": "https://progmiscon.org/misconceptions/Python/VariablesHoldObjects",
"relation": "close-match"
}
] | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.strings.plus-adds-before-concatenating | https://open-misconceptions.github.io/miscon-data/m/programming.strings.plus-adds-before-concatenating | 71cc8015-8e64-4cbf-aec0-1227ef5023f9 | 0.1.1 | draft | low | Plus adds numbers before it concatenates | In an expression that mixes strings and numbers with +, the numbers are added together first and the string is attached afterwards. | overgeneralization | programming.strings | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.strings.concatenation-order"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "predict a left-to-right mixed concatenation",
"signature": "adds the numeric operands regardless of their position",
"example": {
"item": "System.out.println(\"x\" + 1 + 2);",
"expected": "x12",
"response": "x3"
}
}
] | {
"vs_slip": "Consistent across items; the learner explains that 'plus means add'. A slip is one wrong prediction."
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.strings.concatenation-order",
"label": "Operators of equal precedence apply left to right"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/pro... | [
{
"scheme": "progmiscon",
"code": "Java/ArithmeticPlusPrecedes",
"uri": "https://progmiscon.org/misconceptions/Java/ArithmeticPlusPrecedes",
"relation": "close-match"
}
] | {
"sources": [
{
"type": "inventory",
"citation": "Chiodini, L., Moreno Santos, I., Gallidabino, A., Tafliovich, A., Santos, A. L., & Hauswirth, M. (2021). A curated inventory of programming language misconceptions. In Proceedings of the 26th ACM Conference on Innovation and Technology in Computer Sci... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.types.integer-division-gives-fraction | https://open-misconceptions.github.io/miscon-data/m/programming.types.integer-division-gives-fraction | f884573f-e177-4865-9cbb-e334397e406a | 0.1.1 | draft | low | Dividing two integers gives a fraction | Dividing one whole number by another gives the exact mathematical result with a fractional part, whatever the types involved. | overgeneralization | programming.types | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.types.integer-division"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "predict the result of integer division in a language that truncates",
"signature": "predicts the exact quotient",
"example": {
"item": "int x = 7 / 2;\nSystem.out.println(x);",
"expected": "3",
"response": "3.5"
}
},
{
"item_shape": "compute an average of i... | {
"vs_slip": "Consistent across items; the learner is surprised by 3 and cannot explain it. A slip is forgetting a cast once while knowing the rule."
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.types.integer-division",
"label": "Dividing two integers gives an integer result"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.... | null | {
"sources": [
{
"type": "paper",
"citation": "Qian, Y., & Lehman, J. (2017). Students' misconceptions and other difficulties in introductory programming: A literature review. ACM Transactions on Computing Education, 18(1), Article 1.",
"doi": "10.1145/3077618",
"note": "Integer division a... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.variables.assignment-is-equation | https://open-misconceptions.github.io/miscon-data/m/programming.variables.assignment-is-equation | 1d678f7e-ebf2-49bf-979f-eb433148cc0e | 0.1.1 | draft | low | Assignment states an equation | The equals sign in an assignment states that the two sides are equal, as in algebra, so x = x + 1 is a contradiction and a = b and b = a mean the same thing. | misapplied-analogy | programming.variables | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.variables.assignment"
}
] | [
"secondary",
"undergraduate",
"adult"
] | en | [
{
"item_shape": "trace an assignment whose right-hand side uses the variable being assigned",
"signature": "declares the statement impossible or leaves the variable unchanged",
"example": {
"item": "x = 5\nx = x + 1\nWhat is x?",
"expected": "6",
"response": "'Impossible, x can't equal... | {
"vs_slip": "Consistent across items; the learner uses the words 'equals' or 'is the same as' and objects to x = x + 1. A slip is a wrong final value with an otherwise correct trace.",
"vs": {
"programming.variables.assignment-links-variables": "Linkers accept a = b as directional but expect later changes to b... | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.variables.assignment",
"label": "Assignment copies a value into a variable at one moment"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/prog... | [
{
"scheme": "progmiscon",
"code": "Java/AssignCompares",
"uri": "https://progmiscon.org/misconceptions/Java/AssignCompares",
"relation": "close-match",
"note": "progmiscon's entry covers reading = as a comparison; this record covers the underlying algebraic reading."
}
] | {
"sources": [
{
"type": "paper",
"citation": "du Boulay, B. (1986). Some difficulties of learning to program. Journal of Educational Computing Research, 2(1), 57-73.",
"doi": "10.2190/3LFX-9RRF-67T8-UVK9",
"note": "Notional machine difficulties; the equals sign carrying its mathematical m... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.variables.assignment-links-variables | https://open-misconceptions.github.io/miscon-data/m/programming.variables.assignment-links-variables | 3c50552e-a1f7-4d39-b0e5-1e1673032c7b | 0.1.1 | draft | low | Assignment links two variables | After a = b the two variables are connected, so whenever b changes later, a changes too. | misapplied-analogy | programming.variables | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.variables.assignment"
}
] | [
"secondary",
"undergraduate",
"adult"
] | en | [
{
"item_shape": "trace a change to the source variable after an assignment between primitives",
"signature": "reports the destination variable as having the source's new value",
"example": {
"item": "a = 1\nb = a\na = 7\nWhat is b?",
"expected": "1",
"response": "7"
}
}
] | {
"vs_slip": "A slip gives the wrong value once. The belief is stated ('b is a now') and holds on every item where the source is later reassigned.",
"vs": {
"programming.variables.assignment-is-equation": "Equation believers object to x = x + 1; linkers do not.",
"programming.objects.assignment-copies-objec... | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.variables.assignment",
"label": "Assignment copies a value into a variable at one moment"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/prog... | null | {
"sources": [
{
"type": "paper",
"citation": "Ma, L., Ferguson, J., Roper, M., & Wood, M. (2007). Investigating the viability of mental models held by novice programmers. In Proceedings of the 38th SIGCSE Technical Symposium on Computer Science Education (SIGCSE '07), 499-503.",
"doi": "10.1145... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.variables.assignment-moves-value | https://open-misconceptions.github.io/miscon-data/m/programming.variables.assignment-moves-value | 55c0374e-b4f9-4b70-aef3-8d020d2c99c1 | 0.1.1 | draft | low | Assignment moves the value out of the source | Assigning a = b moves the value from b into a, so b is empty or zero afterwards. | misapplied-analogy | programming.variables | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.variables.assignment"
}
] | [
"secondary",
"undergraduate",
"adult"
] | en | [
{
"item_shape": "trace the source variable after an assignment",
"signature": "reports the source as empty, zero or undefined",
"example": {
"item": "b = 4\na = b\nWhat is b?",
"expected": "4",
"response": "0 (or 'nothing')"
}
}
] | {
"vs_slip": "Consistent across items; the learner explains that the value 'went into' the other variable. A slip does not empty the source.",
"vs": {
"programming.variables.assignment-links-variables": "Linkers keep both variables and couple them; movers empty the source."
}
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.variables.assignment",
"label": "Assignment copies a value into a variable at one moment"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/prog... | null | {
"sources": [
{
"type": "paper",
"citation": "Bayman, P., & Mayer, R. E. (1983). A diagnosis of beginning programmers' misconceptions of BASIC programming statements. Communications of the ACM, 26(9), 677-679.",
"doi": "10.1145/358172.358408",
"note": "LET statements understood as moving ... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
programming.variables.names-meaningful-to-machine | https://open-misconceptions.github.io/miscon-data/m/programming.variables.names-meaningful-to-machine | b34639bb-e7b4-400a-bd2a-ced15052078b | 0.1.1 | draft | low | The computer understands variable names | The name of a variable tells the computer what it is for, so a variable called total will add things up and one called largest will hold the biggest value. | misapplied-analogy | programming.variables | [
{
"scheme": "Miscon",
"uri": "https://open-misconceptions.github.io/miscon-data/c/programming.variables.naming"
}
] | [
"secondary",
"undergraduate"
] | en | [
{
"item_shape": "predict the value of a descriptively named variable that is never updated",
"signature": "predicts the value the name suggests rather than the value assigned",
"example": {
"item": "largest = 0\nfor n in [4, 9, 2]:\n pass\nprint(largest)",
"expected": "0",
"response... | {
"vs_slip": "The prediction follows the name on every item, and renaming the variable to x changes the learner's answer. A slip does not depend on the name."
} | {
"conflicts_with": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programming.variables.naming",
"label": "Identifiers are labels with no meaning to the machine"
}
],
"resolved_by": [
{
"external": "https://open-misconceptions.github.io/miscon-data/c/programmin... | null | {
"sources": [
{
"type": "paper",
"citation": "Pea, R. D. (1986). Language-independent conceptual \"bugs\" in novice programming. Journal of Educational Computing Research, 2(1), 25-36.",
"doi": "10.2190/689T-1R2A-X4W4-29J2",
"note": "Egocentrism bug: attributing interpretive intelligence ... | {
"changelog": [
{
"version": "0.1.1",
"date": "2026-09-05T00:00:00",
"change": "Schema 0.2 migration: about/alignments carry a free-string scheme (corestandards.org URLs relabelled CCSS where present); trust computed from reviews[] (none yet, so low); no change to the statement or evidence."
... | CC-BY-4.0 | null | null |
End of preview. Expand in Data Studio
Open Misconceptions
A public catalogue of misconceptions with stable IDs. Each row is one record: a belief a learner could hold, its kind, the evidence pattern that reveals it (with a concrete example), discriminators against slips and neighbouring misconceptions, alignments to external schemes, and provenance.
This dataset mirrors dist/miscon.jsonl from the tagged release of
https://github.com/open-misconceptions/miscon-data. The canonical form of a record is
its stable URI, for example
https://open-misconceptions.github.io/miscon-data/m/math.fractions.add-across.
Provenance caveat
Most records are status: draft with trust: low: drafted from the cited
literature and not yet reviewed. Check status, trust and reviews
before treating a record as settled. reviewed records carry a human
accept or an attested review; trust is computed from the reviews against
the repository's reviewer registry.
Fields
| Field | Meaning |
|---|---|
id |
Stable ID (math.fractions.add-across). Cite as miscon:<id>. |
uri |
Stable URI. |
uuid |
Opaque identifier; the CASE CFItem.identifier. |
version, status, trust |
Record semver; lifecycle (draft, llm-reviewed, reviewed, deprecated, merged); computed trust (low, medium, high). |
title, statement, notes |
Short label, the belief as the learner holds it, and optional notes such as likely origins. |
kind |
Mechanism: overgeneralization, undergeneralization, procedural-bug, notation-confusion, misapplied-analogy. |
domain, about, level_band, locale |
Subject, concepts, education levels, language. |
evidence_patterns |
List of {item_shape, signature, example{item, expected, response}}. |
discriminators |
vs_slip and vs{<neighbour-id>: text}. |
relations |
conflicts_with, resolved_by, and provisional confusable_with, specializes, co_occurs_with, blocked_by. |
alignments |
{scheme, code, uri, relation, note} into CCSS, progmiscon, etc. |
provenance |
{sources[], origin, notes}. |
reviews, history, license |
Reviews (kind, by, date, scope, verdict), merge/supersede history and changelog, always CC-BY-4.0. |
Full field documentation: https://github.com/open-misconceptions/miscon-data/blob/main/schema/README.md.
Load
from datasets import load_dataset
ds = load_dataset("open-misconceptions/miscon-data")
Cite
Concept DOI (latest release): https://doi.org/10.5281/zenodo.22416011. Each release also has a version DOI (v0.1.1: https://doi.org/10.5281/zenodo.22416012). Author and title metadata are in CITATION.cff in the repository.
Licence
CC BY 4.0. Attribute "Open Misconceptions (Vikram Maram and contributors)" and link to the repository or the record URI.
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