Exercise and heart attacks. Does regular exercise reduce the risk of a heart attack?

To answer this question a researcher finds 4000 men over 40 who have not had heart attacks and are willing to participate in a study. She assigns 2000 of the men to a regular program of supervised exercise. The other 2000 continue their usual habits. The researcher follows both groups for 5 years. Outline the design of this study using a diagram like Figures 5.2 and 5.3.

AppendixLO1