Investigators wish to examine if hepatitis B infection is a

Investigators wish to examine if hepatitis B infection is a confounder or an effect modifier for the relationship between drinking and liver cirrhosis. In order to examine these relationships, they enrolled 275 drinkers and 209 non-drinkers in a cohort study. Of those who drink, 183 developed cirrhosis during their lifetime. Of the 209 non-drinkers, only 80 developed cirrhosis in their lifetime. What is the odds ratio of being a drinker compared to being a non-drinker?

Select one:

a. 3.21

b. 2.78

c. 9.85

d. 1.19

Solution

Note that

odds ratio = N(Drinker with Cirrhosis) N(Non Drinker without Cirrhosis) / [N(Drinker without Cirrhosis) N (Non Drinker with Cirrhosis)

Thus,

Odds ratio = 183*129 / [92*80]

= 3.21 [OPTION A]