A variety of sources suggest that individuals assess their health, at least in part, by estimating their percentage of body fat. A widely accepted measure of body fat uses an underwater weighing technique. There are, however, more convenient methods using only a scale and a measuring tape. An article in the Journal of Statistics Education by Roger W. Johnson explored regression models to predict body fat. The file entitled Bodyfat lists a portion of the data presented in the cited article.

a. Use best subsets stepwise regression to establish the relationship between body fat and the variables in the specified file.

b. Predict the body fat of an individual whose age is 21, weight is 170 pounds, height is 70 inches, chest circumference is 100 centimeters, abdomen is 90 centimeters, hip is 105 centimeters, and thigh is 60 centimeters around.