4.22 The ages (in days) at time of death for samples of 11 girls and 16 boys
who died of sudden infant death syndrome are shown in Table E4.22.
Calculate separately for boys and girls the 95% confidence interval for
the (population) mean of age (in days) at time of death.
TABLE E4.22
Females Males
53 46 115
56 52 133
60 58 134
60 59 175
78 77 175
87 78
102 80
117 81
134 84
160 103
277 1144.23 A study was conducted to investigate whether oat bran cereal helps to
lower serum cholesterol in men with high cholesterol levels. Fourteen
men were randomly placed on a diet that included either oat bran or
cornflakes; after two weeks, their low-density-lipoprotein (LDL) choles-
terol levels were recorded. Each man was then switched to the alternative
diet. After a second two-week period, the LDL cholesterol level of each
person was recorded again. The data are shown in Table E4.23. Calcu-
TABLE E4.23
LDL (mmol/L)
Subject Cornflakes Oat Bran
1 4.61 3.84
2 6.42 5.57
3 5.40 5.85
4 4.54 4.80
5 3.98 3.68
6 3.82 2.96
7 5.01 4.41
8 4.34 3.72
9 3.80 3.49
10 4.56 3.84
11 5.35 5.26
12 3.89 3.73
13 2.25 1.84
14 4.24 4.14EXERCISES 181