What Is the Difference Between Absolute & Relative Risk Reduction?

Absolute Risk

• Absolute risk is the chance of something happening irrespective of any other variables. For example, you have a 50 percent chance of getting "heads" in a coin toss, and you have a 10 percent chance of suffering from migraine headaches if you live in the US.

Relative Risk

• Relative risk is risk relative to other relevant variables. For example, if you live in the US, you are three times more likely to suffer from migraines if you are a woman than if you are a man.

Interpreting Risk

• It is important to remember that relative risk does not represent the actual likelihood of an event occurring, it only represents the likelihood of the event relative to another event. If you are trying to determine the likelihood of a particular event, you also evaluate relative risk.

Uses of Relative Risk

• Relative risk is often helpful in medical settings when determining treatment options. For example, studies might show that one drug reduces the symptoms of lung cancer by 50 percent. However, this effectiveness might be reduced for patients suffering from diabetes, causing the relative effectiveness for patients on the drug with diabetes to be only 10 percent. Doctors evaluate the relative effect of a patient's conditions and treatment options to determine the most effective course of action.