risk difference

The difference between the probability of an outcome in the intervention group and the probability of the same outcome in the control group.

Note 1: For example, if the results of a trial were that the probability of death was 0.25 in the control group and 0.10 in the intervention group, the risk difference would be 0.25 - 0.10 = 0.15.

Note 2: Using epidemiology terminology, risk difference would occur between exposed and unexposed groups, rather than intervention and control groups.

Syn.: absolute risk reduction

(Related concepts: number needed to treat, odds ratio and relative risk reduction)