standard_description: Use measures of center and measures of variability for numerical data from random samples to draw informal comparative inferences about two populations. For example, decide whether the words in a chapter of a seventh-grade science book are generally longer than the words in a chapter of a fourth-grade science book.
problem_activity: Task
Ari has collected data on how much her classmates study each week and how well they did on their recent math test. Here is part of the data, showing the percentage of each group (divided according to hours spent studying) who got different grades on the test:
{"table": [{"_attributes": {"class": ["regular"]}, "tbody": [{"tr": [{"th": [{"_value": "Weekly Hours $w$ Studying"}, {"_value": "C or below on test"}, {"_value": "B on test"}, {"_value": "A on test"}]}, {"td": [{"_value": "$w \\lt$ 3"}, {"_value": "50%"}, {"_value": "20%"}, {"_value": "30%"}]}, {"td": [{"_value": "$3 \\leq w \\lt 6$"}, {"_value": "60%"}, {"_value": "25%"}, {"_value": "15%"}]}, {"td": [{"_value": "$w \\geq 6$"}, {"_value": "60%"}, {"_value": "20%"}, {"_value": "20%"}]}]}]}]}
What can you conclude about the percentage of Ari's classmates who got B's? What about the percent who got A's?
Looking at the table, Ari decides that in order to do well in her math class, she should not study more than 3 hours a week: she has a 30 percent chance of getting an A as long as she does not study more than 3 hours per week. Is Ari's reasoning valid?


aligns: no