Question: Refer to Exercise. Find a 95% confidence interval for the difference in population proportions of male policemen and men of other occupations who have heart disease. On the basis of this confidence interval, is it safe to conclude that male police officers are more likely to experience heart disease than other men? Explain.
Exercise: A study reported in the Journal of Occupational and Environmental Medicine (Franke et al., 1998, 40: 441-444) found that retired male Iowa policemen are more likely to have heart disease compared to other men with similar ages but different occupations. Data from the study were that about 32% of a sample of 232 retired policemen had heart disease but only 18% of a sample of 817 men with other occupations had heart disease.
a. Do you think that we can attribute the observed difference in heart disease percentages to job-related factors? Explain.
b. Using a bar chart, graphically compare the policemen and the other men.
c. Calculate a 95% confidence interval for the proportion of retired Iowa policemen who have heart disease.
d. Calculate a 95% confidence interval for the proportion of other retired men who have heart disease.
e. Why are the widths of the two confidence intervals different from each other?