Which of the following sources of bias may be problematic in pretest-posttest designs?
A) history effects
B) testing effects
C) group differences
D) all of the above

Question

Quizplus · Accepted Answer

All of the listed sources of bias can be problematic in pretest-posttest designs: history effects can occur due to events outside the study, testing effects can result from the influence of taking the pretest on posttest performance, and group differences can affect the validity of comparisons between groups.

Which of the Following Sources of Bias May Be Problematic