Centre for Excellence in Teaching and Learning (CETL)

RLO: Relative Risk Reduction (RRR) and Absolute Risk Reduction (ARR)

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Glossary:

Control event rate (CER) = proportion of patients who experience an outcome in the control group.
Experimental event rate (EER) = proportion of patients who experience an outcome in the experimental group.
Relative risk reduction (RRR) = difference in event rates relative to (or proportional to) in the control event rate, expressed as a percentage
RRR = (CER – EER) / CER.
Absolute risk reduction (ARR) = arithmetic difference between the control event rate and the experimental event rate, expressed as a percentage.
ARR = CER - EER

Related concepts:

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