Relative risk

Relative risk (RR), also known as risk ratio, is a statistical term that is 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 measure of risk that compares the risk in two different groups of people.

Definition

Relative risk is defined as the ratio of the probability of an event occurring in an exposed group to the probability of the event occurring in a comparison, non-exposed group. It is used in medical research to determine if an exposure is a risk factor for a particular disease or condition.

Calculation

The calculation of relative risk involves dividing the probability of the event occurring in the exposed group by the probability of the event occurring in the non-exposed group. This can be represented mathematically as:

RR = (Incidence in Exposed Group) / (Incidence in Non-Exposed Group)

Interpretation

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

Uses

Relative risk is used in epidemiological studies, such as cohort studies and case-control studies, to identify and quantify the relationship between exposure and outcome. It is also used in public health to determine the impact of a specific risk factor on a population.

Limitations

While relative risk is a useful measure in epidemiology, it has several limitations. It does not take into account the baseline risk of the event, and it can be influenced by confounding factors. Additionally, 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
• Confounding
• Epidemiology
• Cohort study
• Case-control study

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