The nurse is conducting research on the relative risk of acquiring lung cancer as a result of being ...

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Relative risk ratio compares the incidence rate of a group exposed to a certain risk factor with the incidence rate of a group not exposed to the risk factor. It is calculated by dividing the incidence rate in the exposed group by the incidence rate in the nonexposed group. In this case, we need to first calculate the separate incidence rates for Group A and Group B and then divide to find the relative risk ratio. The incidence rate for Group A is calculated as follows: 20/400 = 0.05  1,000 = 50 cases per 1,000 population. The incidence rate for Group B is calculated as follows: 2/400 = 0.005  1,000 = 5 cases per 1,000 population. The relative risk ratio, then, is calculated as follows: 50/5 = 10.