**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

### Other articles related to "risk, relative risk, risks":

... Another worked example is as follows Example 1

**risk**reduction Example 2

**risk**increase Experimental group (E) Control group (C) Total (E) (C) Total Events (E. 1 Example 2 CER − EER < 0 absolute

**risk**reduction ARR (−)0.3, or (−)30% N/A > 0 absolute

**risk**increase ARI N/A 0.1, or 10% (CER − EER) / CER < 0

**relative risk**...

... Example 1

**risk**reduction Example 2

**risk**increase Experimental group (E) Control group (C) Total (E) (C) Total Events (E) EE = 15 CE = 115 ... EE = 75 CE = 175 ... Non-e ... Example 1 Example 2 CER − EER < 0 absolute

**risk**reduction ARR (−)0.3, or (−)30% N/A > 0 absolute

**risk**increase ARI N/A 0.1, or 10% (CER − EER ...

... Example 1

**risk**reduction Example 2

**risk**increase Experimental group (E) Control group (C) Total (E) (C) Total Events (E) EE = 15 CE = 115 ... EE = 75 CE ... Example 1 Example 2 CER − EER < 0 absolute

**risk**reduction ARR (−)0.3, or (−)30% N/A > 0 absolute

**risk**increase ARI N/A 0.1, or 10% (CER − EER) / CER < 0

**relative risk**reduction RRR (−)0.75 ...

1994 study (845/961 ABC cases/controls) results indicated an associated

**relative risk**of 1.5 (1.2 – 1.9) among women who had given birth before having an abortion ... This was reflected in higher

**risks**for women younger than 18 or older than 30 years of age who have had abortions after 8 weeks' gestation ... found that abortion was associated with a

**relative risk**value of 1.2 (1.0 – 1.5) ...

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