the rate (risk) of poor outcomes in the intervention group divided by the rate of poor outcomes in the control group. For example, if the rate of poor outcomes is 20 per cent in the intervention group and 30 per cent in the control group, the relative risk is 0.67 (20 per cent divided by 30 per cent). The relative risk is 1 when the intervention has no effect, below 1 when it does good and above 1 when it does harm (see Absolute risk reduction).