Odds Ratio

This is a measure of the association between a predictor (or independent) variable and a yes or no binary outcome (or dependent) variable. A value of exactly 1.0 corresponds to no observed association; values of less than 1.0 indicate that the outcome appears to be less likely when the predictor is present or when its value is higher; and values greater than 1.0 indicate that the outcome appears to be more likely when the predictor is present or its value is higher. For a numeric predictor, the odds ratio pertains to a one unit increase in the value of the predictor, and the assumption is that this is the same no matter whether the one unit increase is from 0 to 1, 10 to 11, or 987 to 988 (this is the linearity assumption). The odds ratio is not the same as the relative risk, although it is a good approximation when the outcome is rare; see association measures for binary outcomes [to include relative risk, prevalence ratio, risk difference, and number needed to treat and to explain that OR is not as concretely interpretable, but has advantages in multivariate modeling settings. Should also include a discussion of utility of the OR in the context of a case-control study] with additional discussion of Exposure Odds? vs IncidenceMove Odds..