ABSTRACT
This chapter and the next one concern the problem of drawing conclusions about time lag changes from two administrations of either the same test or similar tests some period of time apart. Even when exactly the same test is administered on both occasions, one cannot be certain that a change in score can be taken at face value. As is shown herein, there may have been differences in the motivation of the test takers on the two occasions, differences in the way the test takers perceived the task, differences in the way in which the tests were administered, or differences in the way in which the test takers recorded their answers (i.e., in the test booklet or on a separate answer sheet).
