Content validity is the extent to which a test samples the full range of behavior or knowledge that it is intended to measure. A test with high content validity covers the domain it claims to cover and does not waste items on irrelevant material.

For a final examination in a history course, content validity requires that the questions represent the topics and skills taught in the course rather than obscure side issues or material never presented. For a driving test, the items and tasks should reflect the actual competencies needed for safe driving. Establishing content validity usually involves expert judgment: specialists review the test blueprint and the items to confirm adequate coverage and appropriate emphasis.

Content validity is distinct from other forms of validity. A test can sample its domain well yet still fail to predict future performance (low criterion validity) or fail to measure the theoretical construct it was meant to measure (low construct validity). Still, without content validity the interpretation of scores becomes questionable from the start.

A test that asks the right questions about the right material possesses content validity. That is the foundation on which other forms of validity are built.