There is growing concern over a possible causal link between consumption of diet soda and obesity. Gallup took in 2013 a nationally representative sample of 2027 adults and asked them about their soda consumption. In the sample, 921 adults described themselves as overweight, and 32% of those individuals said that they mostly drink diet soda. The remaining 1106 adults described themselves as about the right weight, and 19% of those individuals said that they mostly drink diet soda. What is the odds ratio of drinking mostly diet soda, using overweight individuals as the target population and about-right-weight individuals as the reference population?

Question

Quizplus · Accepted Answer

The odds ratio is calculated as the odds of the event (mostly drinking diet soda) in the target population (overweight individuals) divided by the odds of the event in the reference population (about-right-weight individuals).
The odds of mostly drinking diet soda among overweight individuals is:
(32/68)/(208/898) = 1.88
The odds of mostly drinking diet soda among about-right-weight individuals is:
(19/81)/(145/961) = 0.56
The odds ratio is then:
1.88/0.56 = 3.36
Rounding to one decimal place, the odds ratio is 2.0.

There Is Growing Concern Over a Possible Causal Link Between