What is the factor that makes the between-participants posttest-only design a "strong" experimental design and the nonequivalent posttest-only design a weak design?
A) the between-participants posttest-only design involves manipulating variables and the nonequivalent posttest-only design does not
B) testing participants twice changes their performance in the nonequivalent posttest- only design
C) the between participants posttest-only design uses two groups of different participants and the nonequivalent posttest-only design used the same participants
D) random assignment helps insure that the two experimental groups are essentially Equivalent at the outset

Question

Quizplus · Accepted Answer

Random assignment is a key factor in establishing the internal validity of an experiment. It helps ensure that any differences observed between groups can be attributed to the manipulation of the independent variable rather than pre-existing differences between the groups. This is what makes the between-participants posttest-only design strong, as it typically incorporates random assignment, whereas the nonequivalent posttest-only design does not, making it weaker in terms of internal validity.

What Is the Factor That Makes the Between-Participants Posttest-Only Design