Noting marked increases in weight across the population, researchers, nutritionists, and physicians have struggled to find ways to stem the tide of obesity in many Western countries. They have advocated a number of exercise programs, and there has been a flurry of research to determine the effectiveness of these programs. Pretend that you are in charge of a research study to examine the effects of an exercise program on weight loss in comparison with a program that does not involve exercise. 

a. Describe how you could study the exercise program using a between-groups research design. 

b. Describe how you could study the exercise program using a within-groups design. 

c. What is a potential confound of a within-groups design?