Question: Exercise described a study in which men were classified according to how many anger symptoms they exhibit and whether they have coronary heart disease or not. Among 559 men with the most anger symptoms, 59 had coronary heart disease. Among 199 men with no anger symptoms, 8 had coronary heart disease.

a. For those with the most anger symptoms, what is the relative risk of heart disease (compared to those with no anger symptoms)?

b. For those with the most anger symptoms, what is the percent increase in the risk of heart disease?

c. Calculate the odds ratio that compares the odds of having heart disease for the men with the most anger symptoms to the odds for men with no anger symptoms.

Exercise: 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.