Many studies have been conducted on the effects of having a pet on the response to medical problems and on mental health. But doctors in Berlin were interested in the effects of having a pet bird on lung cancer. (I assume they were wondering if birds might cause air pollution that could lead to lung cancer.) They asked 239 patients with lung cancer and 429 controls without lung cancer whether they had a pet bird. Ninety eight of the 239 patients did have a bird, while 101 of the 429 controls had a bird. (That strikes me as a very high percentage of bird owners, but those are the data.)
We really do need a measure of effect size in this example. What would be an appropriate one?
A) the mean difference between bird owners and bird nonowners
B) the squared correlation between ownership and cancer
C) the odds ratio
D) relative risk

Question

Quizplus · Accepted Answer

The odds ratio is the most appropriate measure of effect size in this case because it allows us to compare the odds of having a bird among lung cancer patients versus controls without lung cancer. This measure takes into account the fact that the proportion of bird owners could be different in the two groups and controls for potential confounding variables. A and B are not appropriate measures of effect size because they do not take into account the binary nature of the variable (having a bird or not having a bird). D is not the best choice because it is not as commonly used in case-control studies as the odds ratio.

Many Studies Have Been Conducted on the Effects of Having