Table 9.19 is based on a study with British doctors.
a. For each age, find the sample coronary death rates per 1000 person-years for nonsmokers and smokers. To compare them, take their ratio and describe its dependence on age.
b. Fit a main-effects model for the log rates having four parameters for age and one for smoking. In discussing lack of fit, show that this model assumes a constant ratio of nonsmokers’ to smokers’ coronary death rates over age.
c. From part (a), explain why it is sensible to add a quantitative interaction of age and smoking. For this model, show that the log ratio of coronary death rates changes linearly with age. Assign scores to age, fit the model, and interpret.
TABLE 9.19 Data for Problem
Â
Person-Years
Coronary Deaths
Age
Nonsmokers Smokers
35-44
18,793
52,407
2
32
45-54
10,673
43,248
12
104
55-64
5710
28,612
28
206
65-74
2585
12,663
186
75-84
1462
5317
31
102
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