In a logistic regression analysis, what does the odds ratio indicate?

The odds ratio in a logistic regression analysis quantifies the change in odds of the outcome occurring for a one-unit increase in the predictor variable, holding all other variables constant. Specifically, it measures the likelihood of an event occurring versus it not occurring, providing a clear sense of how much more (or less) likely the event becomes with a change in the predictor.

For example, if the odds ratio for a specific predictor is 1.5, it indicates that for each one-unit increase in that predictor, the odds of the event (such as a disease outcome) increase by 50%. Conversely, an odds ratio of less than 1 would show a decrease in the odds of the event occurring.

This interpretation is fundamental in healthcare statistics, particularly in scenarios like epidemiological studies, where understanding the relationship between potential risk factors and health outcomes is essential.