# Odds ratio estimates

Odds ratios are the increase or decrease in odds associated with a change of the predictor, all other predictors been held constant.

Although mathematically the log odds ratios are easier to work with, when it comes to interpretation, it is more natural to use the odds ratios. Unlike the log odds ratio, the odds ratio is always positive. A value of 1 indicates no change. Values between 0 and less than 1 indicate a decrease in the probability of the outcome event. Values greater than 1 indicate an increase in the probability of the outcome event.

When the predictor variable is a categorical variable, the odds ratio is the increase or decrease in odds over the baseline category.

When a predictor variable is a continuous variable, the odds ratio is the increase or decrease in odds for a change in the predictor variable. The default is for a 1 unit change in the predictor, although it may be more appropriate to use a larger unit, such as for a change of 10 units of the predictor variable.

When a term includes an interaction, the odds ratio will depend on the interacting variables' values, so you will need to use multiple odd ratios to describe the behavior at different levels of interest.

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Version 6.15

Published 18-Apr-2023