Introductory Biostatistics

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