In aviation, “validity” usually refers to the relation between a set of test scores and scores on a criterion measure. For example, assume that a carrier decides to purchase a personality test to use as part of its selection system. Also assume that the selection system is designed to predict scores on the check ride at the end of training. The carrier must determine the relation between scores on the personality test and scores on the check ride before the scores on the personality test can be used to make hiring decisions. If the carrier finds that the relation (correlation) between scores on the personality test and scores on the check ride is low, then the personality test predicts check ride performance poorly and should be discontinued. In this case, the personality test is said to have low validity. If, however, the test scores correlate highly with performance on the check ride, then the personality test is said to have high validity and may be used in hiring decisions.