Regression to the mean is a threat to the internal validity of the pretest/posttest design whenever
A) a long time transpires between the two observation periods.
B) program participants get older between the two observations.
C) people are chosen for a program because initial observations showed that they needed the program more than others did.
D) evaluators gain experience making the observations for the pretest and the posttest.

Question

Quizplus · Accepted Answer

Regression to the mean occurs when extreme or unusual scores on a pretest move towards the mean on a posttest. If program participants are chosen because they have extreme or unusual pretest scores, then regression to the mean could be mistaken for program effects.

Regression to the Mean Is a Threat to the Internal