RR, relative risk
The risk ratio is the probability of an outcome in one treatment comparison group divided by the probability in another.
It is commonly used as a measure of the relative effectiveness of treatments.
For example, if 20 out of 100 participants (20%) die in one treatment comparison group and 50 out of 100 (50%) die in the other group, the risk ratio is 20/50 = 0.40.
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