Answer
If the control group arrived at the same moment as the running group, then the experimenters were sure that the students did not go exercising in the morning before breakfast. This control group is necessary, for a group to compare the experimental group to is needed.
Work Step by Step
If the control group arrived at the same moment as the running group, then the experimenters were sure that the students did not go exercising in the morning before breakfast. This control group is necessary, for a group to compare the experimental group to is needed.