In assessment instruments, the concept of validity relates to how well a test measures what it is purported to measure. Validity may refer to the test items, interpretations of the scores derived from the assessment or the application of the test results to educational decisions. The measurement of an instrument’s validity is often subjective, based on experience and observation.
If an assessment has face validity, this means the instrument appears to measure what it is supposed to measure. Face validity is strictly an indication of the appearance of validity of an assessment. An instrument would be rejected by potential users if it did not at least possess face validity. No professional assessment instrument would pass the research and design stage without having face validity. However, informal assessment tools may lack face validity. For example, online surveys that are obviously meant to sell something rather than elicit consumer data do not have face validity. This is obvious by looking at the survey that its intention is not the same as its stated purpose. Moreover, this lack of face validity would likely reduce the number of subjects willing to participate in the survey.
Content validity concerns whether the content assessed by an instrument is representative of the content area itself. For example, a math assessment designed to test algebra skills would contain relevant test items for algebra rather than trigonometry. Content validity is usually determined by experts in the content area to be assessed.
Construct validity refers to whether the method of assessment will actually elicit the desired response from a subject. Two types of construct validity are convergent and discriminant. If an assessment yields similar results to another assessment intended to measure the same skill, the assessment has convergent validity. If an assessment yields dissimilar results compared to an assessment it should be dissimilar to, it is said to have discriminant validity. Discriminant validity is the extent to which a test does not measure what it should not.
Criterion validity of a test means that a subject has performed successfully in relation to the criteria. Two types of criterion validity are predictive and concurrent validity. Predictive validity concerns how well an individual’s performance on an assessment measures how successful he will be on some future measure. The SAT is an assessment that predicts how well a student will perform in college. Concurrent validity refers to how the test compares with similar instruments that measure the same criterion.
Validity of Results
There are three types of validity primarily related to the results of an assessment: internal, conclusion and external validity. If an assessment has internal validity, the variables show a causal relationship. Conclusion validity means there is some type of relationship between the variables involved, whether positive or negative. External validity involves causal relationships drawn from the study that can be generalized to other situations.