**Relative Risk**

In statistics and mathematical epidemiology, **relative risk (RR)** is the risk of an event (or of developing a disease) relative to exposure. Relative risk is a ratio of the probability of the event occurring in the exposed group versus a non-exposed group.

Risk | Disease status | |
---|---|---|

Present | Absent | |

Smoker | ||

Non-smoker |

Consider an example where the probability of developing lung cancer among smokers was 20% and among non-smokers 1%. This situation is expressed in the 2 × 2 table to the right.

Here, *a* = 20, *b* = 80, *c* = 1, and *d* = 99. Then the relative risk of cancer associated with smoking would be

Smokers would be twenty times as likely as non-smokers to develop lung cancer.

Another term for the **relative risk** is the **risk ratio** because it is the ratio of the risk in the exposed divided by the risk in the unexposed.

Read more about Relative Risk: Statistical Use and Meaning, Worked Example, See Also

### Famous quotes containing the words relative and/or risk:

“Are not all finite beings better pleased with motions *relative* than absolute?”

—Henry David Thoreau (1817–1862)

“If the only new thing we have to offer is an improved version of the past, then today can only be inferior to yesterday. Hypnotised by images of the past, we *risk* losing all capacity for creative change.”

—Robert Hewison (b. 1943)