Number Needed to Treat, Absolute Risk Reduction, Attributable Risk, Number Needed to Harm

Attributable Risk (AR) and Absolute Risk Reduction (ARR) are how much of the observed change in risk is due to the treatment (or exposure) being studied. Put another way AR is the amount of disease that would be eliminated if the exposure was eliminated. ARR would be the amount of disease that would be eliminated if all patients were receiving the drug. ARR and AR are essential the same thing