If participants in a two-group study are matched on only a few of the relevant characteristics, which of the following is the most serious threat to the study's internal validity?
A) history
B) regression
C) selection by maturation
D) instrumentation

Question

Quizplus · Accepted Answer

When participants are matched on only a few characteristics, differences in maturation rates between groups can lead to differences in outcomes, threatening internal validity.

If Participants in a Two-Group Study Are Matched on Only