Even when pretest scores are the same,on average,for treatment and comparison groups in a nonequivalent control group design,the two groups may not be equivalent because
A) the pretest measure is unlikely to be relevant to the dependent variable.
B) the posttest measure is unlikely to be the same as the pretest measure, and the two groups must be equivalent at the posttest.
C) the fact that the two groups are equal on the pretest measure does not ensure that the groups are equivalent on other characteristics relevant to the study.
D) the natural growth rates of two groups from different populations are likely to be the same, but the pretest estimate of equality may still be in error.

Question

Quizplus · Accepted Answer

Equivalence on a single pretest measure does not guarantee equivalence on other relevant characteristics. Other factors such as demographic characteristics, prior experiences, and motivation may affect the groups differently, even if their pretest scores are the same. Therefore, it is important to consider other sources of potential bias and use methods such as randomization or matching to increase the likelihood of equivalence between groups.

Even When Pretest Scores Are the Same,on Average,for Treatment and Comparison