Use the sign test on the blood cholesterol data in Exercise 10-53. Is there evidence that diet and exercise reduce the median cholesterol level?

Exercise 10-53

Fifteen adult males between the ages of 35 and 50 participated in a study to evaluate the effect of diet and exercise on blood cholesterol levels. The total cholesterol was measured in each subject initially and then three months after participating in an aerobic exercise program and switching to a low-fat diet.