of 793 persons who were involved in bicycle accidents during a one-year
period (Table E4.12).TABLE E4.12
Wearing Helmet
Head Injury Yes No Total
Yes 17 218 235
No 130 428 558
Total 147 646 793(a) Use the data from the group without helmets, calculate the 95%
confidence interval for the proportion of head injury.
(b)Calculate the 95% confidence interval for the odds ratio representing
the relationship between use (or nonuse) of a helmet and head injury.4.13 A case–control study was conducted in Auckland, New Zealand, to
investigate the e¤ects of alcohol consumption on both nonfatal myo-
cardial infarction and coronary death in the 24 hours after drinking,
among regular drinkers. Data were tabulated separately for men and
women (Table E4.13).
TABLE E4.13
Myocardial
Infarction Coronary Death
Drink in the
Last 24 hours Controls Cases Controls Cases
Men No 197 142 135 103
Yes 201 136 159 69
Women No 144 41 89 12
Yes 122 19 76 4(a) Refer to the myocardial infarction data and calculate separately
for men and women the 95% confidence interval for the odds ratio
associated with drinking.
(b)Refer to coronary death data and calculate separately for men and
women the 95% confidence interval for the odds ratio associated
with drinking.
(c) From the results in parts (a) and/or (b), is there any indication that
gendermay act as an e¤ect modifier?4.14 Adult male residents of 13 counties of western Washington in whom
testicular cancer had been diagnosed during 1977–1983 were interviewed
over the telephone regarding both their history of genital tract conditions
EXERCISES 177