The critical criterion that each MDTP test must meet is that knowledge of the content of the topics and ability to answer the test's questions are prerequisites for success in subsequent mathematics courses. Evidence that these criteria are satisfied comes from the acceptance of the tests by hundreds of teachers throughout California.
Further evidence comes from the data collected during extensive field-testing of the tests.
During the final stage of field-testing, the form is administered to students near the beginning of a course so that their test scores can be compared with measures of their performance at the end of the course. For example, the Precalculus Test has been administered at the start of a college calculus course and scores were compared with students' grades in the course. For another example, the Algebra Readiness test has been given to students during the first few weeks of an elementary algebra course and their test scores were compared to both teacher rating of the students' readiness for the next mathematics course at the end of the elementary algebra course and to the students' performance on MDTP's Elementary Algebra Diagnostic Test at the end of the elementary algebra course. A part of the test development process is an extensive review of item statistics to ensure that each item tests appropriate knowledge and skill, that each item discriminates reasonably well between stronger and weaker students, and that the difficulty levels of the items are not too widespread. The R-Biserial is used as a measure of the consistency of an item with the rest of the test.