An experiment that accurately tests the question of whether students can squeeze a clothespin more times in a minute after resting than exercising should include a control group. The control group is a group of participants who do not receive the experimental treatment (in this case, exercising) and are used as a comparison for the experimental group. By comparing the results of the experimental group and the control group, the researchers can determine whether the experimental treatment (exercising) had an effect on the outcome (the number of times the students can squeeze a clothespin in a minute).