Baldness and myocardial infarction, self-assessed baldness. A case–control study was completed to learn about the relationship between male-pattern baldness and the risk of cardiovascular disease.

Cases were men less than 55 years of age hospitalized for a heart attack. Cases were excluded if they had a prior history of serious heart problems. Controls were men with no history of heart disease admitted to the same hospitals for nonfatal, noncardiac problems.

Table 18.21 cross tabulates results according to self-assessed baldness, with baldness graded on a scale of 1 (no baldness) to 5

(extreme baldness).

(a) Calculate the odds ratios associated with each level of baldness.
Interpret your results.

(b) Conduct a chi-square test of association. Report the chi-square statistic, its df, and P-value.

(c) Conduct a test for trend.