In a study comparing two nonequivalent groups, a selection-history confound occurs when
A) some event intervenes between pretest and posttest and affects just one of the groups.
B) some event intervenes between pretest and posttest and affects both selected groups equally.
C) selection influences one of the groups and history influences the other.
D) some historical event causes a failure of the random assignment procedure.

Question

Quizplus · Accepted Answer

A selection-history confound occurs when an external event affects only one of the groups between the pretest and posttest, leading to differences that are not due to the treatment or intervention being studied.

In a Study Comparing Two Nonequivalent Groups, a Selection-History Confound