Answer:
selection-history effect.
Explanation:
Dr. Johannsen wants to test whether recovering alcoholics perform worse on tests of motor coordination than a group of control participants. Unbeknownst to him, the control group meets at an amusement park three hours before testing and goes on as many rides as possible. They perform worse than the alcoholic group. This is an example of a selection-history effect. Selection-history effect is any activity/event that happens before the start of a study, between pretest and posttest that has the ability to change the conditions of a study an hence its outcome.
