Validity refers to whether a test measures what it claims to measure. There are several types of validity including content validity, concurrent validity, and predictive validity. Content validity is established by subject matter experts reviewing test items and determining their alignment with the test's intended content areas. Concurrent validity examines the relationship between test performance and current mastery, while predictive validity looks at the relationship between test performance and future mastery. Establishing validity, particularly content validity, is critical for certification and licensure tests.