Research Measurements
RR
Relative Risk
The ratio of event probability in the treatment group vs. the control group.
Relative risk (RR) compares the probability of an event (such as hair loss improvement) in the treatment group to the probability in the control group. An RR of 1.0 means no difference; RR > 1.0 indicates increased risk (or benefit) with treatment; RR < 1.0 indicates decreased risk. For example, an RR of 0.7 for hair shedding with zinc supplementation means the supplemented group had 30% lower risk of shedding compared to placebo. Relative risk is most informative when considered alongside absolute risk reduction and number needed to treat.