A **rate ratio** (sometimes called an **incidence density 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]}

References

**^***Bellan, Steve. “Study Design and Analysis in Epidemiology: Where does modeling fit?”. Retrieved 8 April 2012.*- ^ Jump up to:
^{a}^{b}*“Rate Ratio”. www.ctspedia.org.*