Test validity

Test validity is the extent to which a test (such as a chemical, physical, or scholastic test) accurately measures what it is supposed to measure. In the fields of psychological testing and educational testing, "validity refers to the degree to which evidence and theory support the interpretations of test scores entailed by proposed uses of tests". Although classical models divided the concept into various "validities" (such as content validity, criterion validity, and construct validity), the currently dominant view is that validity is a single unitary construct.

Validity is generally considered the most important issue in psychological and educational testing because it concerns the meaning placed on test results. Though many textbooks present validity as a static construct, various models of validity have evolved since the first published recommendations for constructing psychological and education tests. These models can be categorized into two primary groups: classical models, which include several types of validity, and modern models, which present validity as a single construct. The modern models reorganize classical "validities" into either "aspects" of validity or "types" of validity-supporting evidence

Although psychologists and educators were aware of several facets of validity before World War II, their methods for establishing validity were commonly restricted to correlations of test scores with some known criterion. Under the direction of Lee Cronbach, the 1954 Technical Recommendations for Psychological Tests and Diagnostic Techniques attempted to clarify and broaden the scope of validity by dividing it into four parts: (a) concurrent validity, (b) predictive validity, (c) content validity, and (d) construct validity. Cronbach and Meehl’s subsequent publication grouped predictive and concurrent validity into a "criterion-orientation", which eventually became criterion validity.

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