Introductory Biostatistics

(Chris Devlin) #1
a¼ 11
r 1 c 1
n

¼


ð 46 Þð 61 Þ
299
¼ 9 : 38
r 1 r 2 c 1 c 2
n^2 ðn 1 Þ

¼


ð 46 Þð 253 Þð 61 Þð 238 Þ
ð 299 Þ^2 ð 298 Þ
¼ 6 : 34
ad
n

¼


ð 11 Þð 203 Þ
299
¼ 7 : 47
bc
n

¼


ð 35 Þð 50 Þ
299
¼ 5 : 85

The process is repeated for each of the other two smoking levels. For moderate
smokers,


a¼ 70
r 1 c 1
n

¼


ð 112 Þð 287 Þ
549
¼ 58 : 55
r 1 r 2 c 1 c 2
n^2 ðn 1 Þ

¼


ð 112 Þð 437 Þð 287 Þð 262 Þ
ð 549 Þ^2 ð 548 Þ
¼ 22 : 28
ad
n

¼


ð 70 Þð 220 Þ
549
¼ 28 : 05
bc
n

¼


ð 42 Þð 217 Þ
549
¼ 16 : 60

TABLE 6.10


Shipbuilding Cases Controls Total


Yes 11 (a)35(b)46ðr 1 Þ
No 50 (c) 203 (d) 253 ðr 2 Þ


Total 61 ðc 1 Þ 238 ðc 2 Þ 299 ðnÞ


220 COMPARISON OF POPULATION PROPORTIONS

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