Participants for a treatment group are chosen because they score very low on a pretest measure of performance.When their performance improves on the posttest,the researcher
A)can be confident that the treatment was effective.
B)can rule out testing and instrumentation threats to internal validity.
C)should consider the possibility that statistical regression influenced posttest scores.
D)must conclude that additive effects with selection are responsible for the outcome.

Question

Quizplus · Accepted Answer

When participants are selected based on extreme scores (in this case, low scores on pretest), there is a high likelihood of statistical regression to the mean. This means that their scores are likely to improve on the posttest simply due to chance, regardless of any treatment effects. Therefore, the researcher should consider the possibility of statistical regression as an alternative explanation for the improvement in posttest scores.

Participants for a Treatment Group Are Chosen Because They Score