In public debate, and sometimes in statutes and regulations as well, we find reference to “valid tests,” but tests themselves are not valid or invalid. Rather, it is an inference based on test scores that is valid or not. A given test might provide good support for one inference but weak support for another. For example, a well-designed end-of-course exam in statistics might provide good support for inferences about students’ mastery of basic statistics but very weak support for conclusions about mastery of mathematics more broadly. Validity is also a continuum: inferences are rarely perfectly
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