(b)OR¼ 0 :26; it supports the conclusion in part (a) showing that hel-
met protection is associated with reduced odds, and so a lower pro-
portion, of head injuries.
1.8 (a)Men: OR¼ 0 :94, indicating a slightly lower risk of myocardial in-
farction. Women: OR¼ 0 :55, indicating a lower risk of myocardial
infarction.
(b)The e¤ect of drinking is stronger in women, reducing the risk more:
45% versus 6%.
(c)Men: OR¼ 0 :57 indicating a lower risk of coronary death; women:
OR¼ 0 :39 indicating a lower risk of coronary death.
(d)The e¤ect of drinking is stronger in women, reducing the risk more:
61% versus 43%.
1.9 (a)Zero or one partner: OR¼ 2 :70; two or more partners: OR¼ 1 :10.
(b)Both odds ratios indicate an elevated risk associated with smoking,
but the e¤ect on those with zero or one partner is clearer.
(c)Combined estimate of odds ratio: ORMH¼ 1 :26.1.15 Sensitivity¼ 0 :733; specificity¼ 0 :972.
1.16 For Dupont’s EIA: sensitivity¼ 0 :938; specificity¼ 0 :988; for Cellular
Product’s EIA: sensitivity¼ 1 :0; specificity¼ 0 :952.
1.17 (a)Heart disease, 30.2%; cancer, 24.1%; coronary disease, 8.2%; acci-
dents, 4.0%; others, 33.4%;(b)population size: 3,525,297;(c)rates per
100,000: cancer, 235.4; coronary disease, 80.3; accidents, 39.2; others,
325.5.
1.19 OR¼ 1 :43.
1.20 (a)For nonsmokers: OR¼ 1 :28;(b)for smokers: OR¼ 1 :61;(c)the risk
seems to be higher for smokers;(d)combined estimate: ORMH¼ 1 :53.
1.21 (a)Odds ratios associated with race (black vs. white, nonpoor):(i)25–
44: 1.07;(ii)45–64: 2.00;(iii) 65 þ: 1.54. Di¤erent ratios indicate
possible e¤ect modifications by age.
(b)Odds ratios associated with income (poor vs. nonpoor, black):(i)
25–44: 2.46;(ii)45–64: 1.65;(iii) 65 þ: 1.18. Di¤erent ratios indicate
a possible e¤ect modification by age.
(c)Odds ratios associated with race (black vs. white) (i) for 65þ
yearsþpoor: 1.18;(ii)for 65þyearsþnonpoor: 1.54. The di¤erence
(1: 1801 :52) indicates a possible e¤ect modification by income.
1.22 (a) Age Group Odds Ratio
25–44 7.71
45–64 6.03
65 þ 3.91500 ANSWERS TO SELECTED EXERCISES