Question: Do grumpy old men have a greater risk of having coronary heart disease than men who aren't so grumpy? Harvard Medical School researchers examined this question in a prospective observational study reported in the November 1994 issue of Circulation (Kawachi et al., 1994). For 7 years, the researchers studied men between the ages of 46 and 90. All study participants completed a survey of anger symptoms at the beginning of the study period. Among 199 men who had no anger symptoms, there were 8 cases of coronary heart disease. Among 559 men who had the most anger symptoms, there were 59 cases of coronary heart disease.

a. Construct a contingency table for the relationship between degree of anger and the incidence of heart disease.

b. Among those with no anger symptoms, what percentage had coronary heart disease?

c. Among those with the most anger symptoms, what percentage had coronary heart disease?

d. Draw a bar graph of these data. Based on this graph, does there appear to be an association between anger and the risk of coronary heart disease? Explain.