Question: Refer to Exercise. What are the explanatory and response variables?

Exercise: Contains one of the complications listed as "difficulties and disasters" with designed experiments or observational studies. Explain the problem and suggest how it could have been either avoided or addressed. If you think more than one complication could have occurred, mention them all, but go into detail about only the most problematic.

Researchers ran an advertisement in a campus newspaper asking for sedentary volunteers who were willing to begin an exercise program. The volunteers were allowed to choose which of three programs they preferred: jogging, swimming, or aerobic dance. After 5 weeks on the exercise programs, weight loss was measured. The joggers lost the most weight, and the researchers announced that jogging was better for losing weight than either swimming or aerobic dance.