Risk ratio

Risk ratio (RR), also known as relative risk, is a statistical measure used in epidemiology to quantify the risk of a certain event happening in one group compared to the risk of the same event happening in another group. It is a useful measure in public health research and clinical trials.

Definition

The risk ratio is defined as the ratio of the probability of an event occurring in the exposed group to the probability of the event occurring in the non-exposed group. It is a measure of the strength of association between an exposure and an outcome.

Calculation

The risk ratio is calculated by dividing the incidence rate of the outcome in the exposed group by the incidence rate in the non-exposed group. The formula is:

RR = (Incidence in exposed group) / (Incidence in non-exposed group)

Interpretation

A risk ratio of 1 indicates no difference in risk between the two groups. A risk ratio greater than 1 indicates an increased risk of the event in the exposed group, while a risk ratio less than 1 indicates a decreased risk.

Limitations

The risk ratio is a relative measure, meaning it only provides information about the relative difference in risk between two groups. It does not provide information about the absolute risk or the actual difference in risk between the two groups.

See also

• Odds ratio
• Hazard ratio
• Confidence interval
• Epidemiology
• Clinical trials

References

Risk ratio Resources
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