Validity

the appropriateness or correctness of inferences, decisions, or descriptions made about individuals, groups, or institutions from test results.

There is no such thing as a generically valid test. Validity must be considered in terms of the correctness of a particular inference about test takers.

Although there are different sources of evidence, validity is a unitary concept. Three types of validity evidence are commonly referred to: Content, Construct and Criterion-related evidence.

Content-related Validity

The sample of questions in a test should represent the important content, skills, or behaviors of the domain of interest. Evidence of content-related validity is usually obtained by having knowledgeable people look at the test items and make judgements about the appropriateness of each item and overall coverage of the domain.

Criterion-related Validity

Sometimes, test results are used to make inferences about how a person might perform on a different domain. Criterion-related evidence is needed to support inferences about a person's current or future performance by demonstrating that test scores are systematically related to other indicators or criteria.

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Construct-related Validity

From test results we make inferences about the degree to which an examinee possesses some trait or theoretical construct. Construct-related validity asks: What do these test scores really mean?

Evidence of construct-related validity involves making hypotheses and collecting information over a period of time, using many sources and methods.

Consequential Aspects of Validity

In addition to ensuring that inferences made from tests are appropriate, the test user should also consider the consequences of using test scores to make decisions.

Are the potential and actual social consequences of test interpretation and use supportive of the intended testing purposes? Are they also consistent with other social values?

Source: Messick. (1989). Validity. In R. Linn (Ed.) Educational Measurement, 3rd. Ed.

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