Odds ratio and relative risk

Abstract

The odds ratio (OR) and relative risk (RR) are commonly reported in research studies. Many clinicians find it difficult to interpret these terms. This article deals with the basic understanding of probability, odds, OR and RR. How to estimate, calculate and interpret these parameters is also discussed. ORs can be calculated for all types of study designs. However, RRs are not applicable for case–control studies and should be reported in prospective study designs such as cohort studies or clinical trials.

Keywords

• probability
• odds
• odds ratio
• relative risk