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# risk ratio

*— The likelihood of an outcome in one treatment comparison group divided by the likelihood in another*

#### Synonyms:

RR, relative risk

#### Full explanation:

The risk ratio is the probability of an outcome in one treatment comparison group divided by the probability in another.

It is commonly used as a measure of the relative effectiveness of treatments.

#### Example:

For example, if 20 out of 100 participants (20%) die in one treatment comparison group and 50 out of 100 (50%) die in the other group, the risk ratio is 20/50 = 0.40.

#### See also:

effectiveness

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