Hospital, Fukuoka, Japan (Table E6.25). For each of the three criteria
(smoking, alcohol, and body mass index), test, at the 5% level, for the
trend of men with gallstones.TABLE E6.25
Number of Men Surveyed
Factor Total with Number Gallstones
Smoking
Never 621 11
Past 776 17
Current 1342 33
Alcohol
Never 447 11
Past 113 3
Current 2179 47
Body mass index
(kg/m^2 )
<22.5 719 13
22.5–24.9 1301 30
b 25 : 0 719 186.26 Prematurity, which ranks as the major cause of neonatal morbidity and
mortality, has traditionally been defined on the basis of a birth weight
under 2500 g. But this definition encompasses two distinct types of
infants: infants who are small because they are born early, and infants
who are born at or near term but are small because their growth was
retarded.Prematurity has now been replaced bylow birth weightto
describe the second type andpretermto characterize the first type (babies
born before 37 weeks of gestation). A case–control study of the epi-
demiology of preterm delivery was undertaken at Yale–New Haven
Hospital in Connecticut during 1977. The study population consisted of
175 mothers of singleton preterm infants and 303 mothers of singleton
full-term infants. In Example 6.16 we have analyzed and found a signif-
icant association between the mother’s age and preterm delivery; that the
younger the mother, the more likely the preterm delivery. Table E6.26
TABLE E6.26
Socioeconomic Level Cases Controls
Upper 11 40
Upper middle 14 45
Middle 33 64
Lower middle 59 91
Lower 53 58
Unknown 5 5EXERCISES 243