9.32 Running and sleep. Sufficient sleep is important for adolescents for both their neural and psychological development. Despite this, daytime sleepiness and poor physical and psychological functioning related to chronic sleep disturbances are common. There is a growing body of evidence that exercise is associated with both better sleep and improved psychological functioning. Sixty participants were recruited from a high school in northwestern Switzerland. They were randomly assigned to either a running group or a con-trol group, 30 to each group. The running group ran every morning for a little over 30 minutes on weekdays for a three-week period. All participants used a sleep log for subjective evaluation of sleep, and sleep was also objectively assessed at the beginning and end of the study using a sleep electroencephalographic device that measured quantities such as sleep efficiency and time spent in the four different sleep phases. Running was found to impact positively on both objective and subjective measures of sleep functioning.

(a)what are the explanatory variable(s) and the response variable(s).

(b) Outline the design of the experiment.

(c) Here are some more details on the treatment and control groups. All participants arrived at school at 7 A . M ., and the running group did two laps on the track and then ran cross country in groups of least four people for 30 minutes. The control group remained seated at the track, worked on homework, and interacted with each other. When the runners returned, all participants prepared for school and ate a breakfast that was provided. Why do you think the experimenters had the control group arrive at 7 A . M ., interact with classmates, and have breakfast together? Explain. Do you think having the control group do these activities is important for the types of conclu-sions that can be reached? How?

(d) Time to sleep onset was measured before the beginning of the study and again at the end of the study for participants in both groups. Can this be considered a randomized controlled experiment with time to sleep onset as the response and four treatments (runners before, runners after, controls before, and controls after)? Explain why or why not.