Introductory Biostatistics

(b)Odds ratios associated with frequent contacts: for physicians, 3.11;

for nurses, 2.80;(c)odds ratios are similar but larger for physicians;

(d)ORMH¼ 2 :93.

1.38 (a)For age:

Group Odds Ratio

14–17 2.09

18–19 1.96

20–24 1.69

25–29 1.02

Yes, the younger the mother, the higher the risk.

(b)For socioeconomic level:

Group Odds Ratio

Upper 0.30

Upper middle 0.34

Middle 0.56

Lower middle 0.71

Yes, the poorer the mother, the higher the risk.

(c)General odds ratio is 0.57: given two mothers with di¤erent eco-

nomic levels, the odds that the richer one having premature delivery

is 0.57. Yes, it supports the results in part (b).

1.39 (a) Group SMR

Male 1.22

Female 0.78

Black 2.09

White 0.85

(b)Relative risks: associated with gender, 1.57; associated with race,

2.47.

1.40 Group Odds Ratio

Protestants 0.50

Catholics 4.69

Others 0.79

Yes, there is clear evidence of an e¤ect modification (4: 6900 : 50 ; 0 :79).

504 ANSWERS TO SELECTED EXERCISES