The adverse outcome (black)<unk>  between the group exposed to the treatment (left) and the group unexposed to the treatment (right) is −0.25 (RD = −0.25, ARR = 0.25). The<unk>  (RD), excess risk, or attributable risk is the<unk>  between the risk of an outcome in the exposed group and the unexposed group. It is computed as , where is the incidence in the exposed group, and is the incidence in the unexposed group. If the risk of an outcome is increased by the exposure, the term absolute risk increase (ARI) is used, and computed as . Equivalently, if the risk of an outcome is decreased by the exposure, the term absolute risk reduction (ARR) is used, and computed as . The inverse of the absolute risk reduction is the number needed to treat, and the inverse of the absolute risk increase is the number needed to harm.
Risk difference
Relative risk reduction
Absolute threshold
Minimal important difference
Indicative limit value
Odds ratio
Hazard ratio
Threshold limit value