Odds Ratio

The odds ratio (OR) is a nonparametric, inferential test of association. It evaluates whether the odds of a certain event (or outcome) happening is the same for two groups. Specifically, the OR measures the ratio of the odds that an event or result will occur to the odds of the event not happening, given one group’s exposure to some factor to which the other group has not been exposed. This entry discusses the use of OR, its assumptions, and its calculation, significance and strength testing for the OR, and interpretation of the OR, giving an example of OR use.

The OR answers the following questions: “What are the odds that a child who has not been vaccinated will contract chicken pox as compared with the odds ...