Answers to Selected Exercises
Chapter 1
1.1 For left-handed:p¼ 0 :517; for right-handed:p¼ 0 :361.1.2 For factory workers:x¼49; for nursing students:x¼73.
1.3 For cases:p¼ 0 :775; for controls:p¼ 0 :724.1.4 For nursing home A: p¼ 0 :250; for nursing home B: p¼ 0 :025. The
proportion in nursing home A where the ‘‘index’’ nurse worked is 10
times higher than the proportion in nursing home B.1.5 (a) For high exposure level:p¼ 0 :488; for low exposure level:p¼ 0 :111.
Students in the high-exposure group have a much higher proportion
of cases, more than four times higher.
(b)OR¼ 7 :66; it supports the conclusion in part (a) showing that high
exposure is associated with higher odds, and so a higher proportion,
of positive cases.1.6 (a) With EFM:p¼ 0 :126; without EFM:p¼ 0 :077. The EFM-exposed
group has a higher proportion of cesarean deliveries.
(b)OR¼ 1 :72; it supports the conclusion in part (a) showing that EFM
exposure is associated with higher odds, and so a higher proportion,
of cesarean deliveries.1.7 (a) With helmet: p¼ 0 :116; without helmet: p¼ 0 :338. The group
without helmet protection has a higher proportion of head injuries.
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