If one or more of the treatments in an experiment is expected to have a large and long-lasting effect that could influence the participants' scores in later treatments, the best strategy is to use a between-subjects design.

Question

Quizplus · Accepted Answer

Using a between-subjects design ensures that each participant is only exposed to one treatment condition, so there is no risk of carryover effects or contamination of later treatments by earlier ones. This is particularly important if one treatment is expected to have a large and long-lasting effect that could influence the participants' scores in later treatments.

If One or More of the Treatments in an Experiment