Validity

Evidence that a test is measuring an intended construct, through investigation of theorized relationships between test scores and other measures. Convergent evidence is supported by positive relation ships between the test scores and another instrument intended to measure a similar construct. Discriminant evidence is supported by a negative or zero relationship between the test scores and another instrument intended to measure a different construct. Both types of evidence are generally supported by correlational data. As an example, scores on a test intended to measure understanding of algebra concepts may be theorized to relate positively with a test of geometry understanding and to relate negatively with a test of reading ability. A positive correlation between the algebra and geometry test scores would be an example of convergent evidence. A negative correlation between the algebra and reading test scores would be an example of discriminant evidence.