Can validity rise when reliability declines?
Applied Measurement in Education 1997; 10:377 387 Feldt challenges the oft-stated deduction from classical test theory that decreased reliability will result in decreased validity. In recent years, advocates of performance-based assessment have almost always argued that the lower reliability of the scores yielded by their instruments, compared with scores from multiple-choice tests, was offset by increases in validity. Feldt describes two conditions under which lowered reliability might reasonably be expected to be associated with increased criterion-related validity, defined as a Pearson product-moment correlation coefficient between test scores and performance on a criterion measure. These are if a test is altered by eliminating elements that cause construct-irrelevant variance in examinee performance and if a test and the criterion measure the same set of factors, but the weighting of factors varies in the two measures. In the two examples he presents using hypothetical data, the va