Biology:Rate ratio

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A rate ratio (sometimes called an incidence density ratio or incidence rate ratio) in epidemiology, is a relative difference measure used to compare the incidence rates of events occurring at any given point in time. A common application for this measure in analytic epidemiologic studies is in the search for a causal association between a certain risk factor and an outcome.[1]

[math]\displaystyle{ \text{Rate Ratio} = \frac{\text{Incidence Rate 1}}{\text{Incidence Rate 2}} }[/math] [2]

Where incidence rate is the occurrence of an event over person-time, for example person-years.

[math]\displaystyle{ \text{Incidence Rate} = \frac{\text{events}}{\text{person time}} }[/math]

Note: the same time intervals must be used for both incidence rates.[2]

See also