Risk is the number of those having the outcome of interest (death, infection, illness, etc) divided by the total number exposed to the treatment Odds is the number having the outcome divided by the number not having the outcome Risk and risk ratios are more commonly used than odds and odds ratios in medicine as these are much more intuitive Risk describes the probability of an event occurring In medicine this is often an undesirable health outcome or adverse event Odds ratio = (A*D) / (B*C) The relative risk tells us the ratio of the probability of an event occurring in a treatment group to the probability of an event occurring in a control group It is calculated as Relative risk = A/ (AB) / C/ (CD) In short, here's the difference An odds ratio is a ratio of two odds
Table I From Prevalence Odds Ratio Versus Prevalence Ratio Choice Comes With Consequences Semantic Scholar
