How is relative risk reduction calculated?

Relative risk reduction is a measure used in epidemiology to quantify the decrease in risk associated with a treatment or intervention compared to a control group. It is calculated by taking the difference in risk between the control and treatment groups, divided by the risk in the control group. The formula for this is:

Relative Risk Reduction (RRR) = (Control Event Rate - Experimental Event Rate) / Control Event Rate.

In simpler terms, if you know the relative risk (the ratio of the probability of an event occurring in the treatment group compared to the control group), the calculation for relative risk reduction becomes:

1 - relative risk.

This demonstrates the proportion by which the risk is reduced due to the treatment when compared to the risk without the treatment. Therefore, the option that states "1 - relative risk" accurately reflects this calculation, making it the correct answer.

The other options do not define relative risk reduction correctly, as they focus on various other measures or misinterpret the relationship between relative risk and risk reduction.