Using pretests to organize groups can be problematic because scores on posttest measures may be affected not (just) by the treatment but by ______.
A) history effects
B) regression to the mean
C) nonequivalent groups
D) individual differences

Question

Quizplus · Accepted Answer

Pretest scores may be affected by random fluctuations, so using them to form groups can result in groups that are not equivalent in terms of the variable being measured. This can lead to regression to the mean, where individuals with extreme pretest scores (either very high or very low) are likely to score closer to the group mean on the posttest, regardless of the treatment they received. Therefore, using pretests to organize groups can make it difficult to determine if any changes on the posttest were due to the treatment or just to chance fluctuations.

Using Pretests to Organize Groups Can Be Problematic Because Scores