1. the characteristic of being founded on truth, accuracy, fact, or law.

2. the degree to which empirical evidence and theoretical rationales support the adequacy and appropriateness of conclusions drawn from some form of assessment. Validity has multiple forms, depending on the research question and on the particular type of inference being made. For example, the three major types of test validity are criterion validity, based on correlation with an accepted standard; construct validity, based on the conceptual variable underlying a test; and content validity, based on the subject matter of a test. Other forms of validity prominent in the social sciences include ecological validity, external validity, internal validity, and statistical conclusion validity. —valid adj.