Test validity refers to the degree to which a test measures what it claims to measure. It ensures that the results of the test accurately reflect the specific skills, knowledge, or traits it is intended to assess. For example, a math test should effectively evaluate a student's mathematical abilities rather than their reading skills. There are several types of validity, including content validity, construct validity, and criterion-related validity. Content validity examines whether the test covers the relevant material, while construct validity assesses whether the test truly measures the theoretical concept it aims to evaluate. Criterion-related validity compares test results with an external standard or criterion.