What does the odds ratio compare?

The odds ratio is a measure used in epidemiology to compare the odds of an event occurring in one group to the odds of the same event occurring in another group. It is particularly useful in case-control studies where the goal is to assess the association between exposure and outcome.

For example, in a study examining the relationship between smoking and lung cancer, the odds ratio would quantify how much more likely individuals who smoke are to develop lung cancer compared to those who do not smoke. The calculation involves the odds of the event (lung cancer) in the exposed group (smokers) and the odds in the non-exposed group (non-smokers).

This measurement allows researchers to evaluate the strength of the association and to infer potential causal relationships, making the odds ratio a pivotal statistic in public health and clinical research. The focus on comparing odds rather than risks is crucial, especially in studies where direct measurement of risk is not feasible.