Final answer:
Incidence rates for groups with varying attributes or exposures are compared to calculate relative risk, which helps determine the association between risk factors and health outcomes in epidemiological studies.
Step-by-step explanation:
When measuring and comparing incidence rates for groups that differ by some attribute or exposure, epidemiologists are often interested in the calculation of relative risk (RR). This is a measure that is used to determine whether there is an association between a particular risk factor and a health outcome. For instance, to evaluate if smoking is related to cardiovascular disease, epidemiologists would compare the incidence of cardiovascular disease between smokers and non-smokers.
Relative risk is quantified by dividing the incidence of a health event in a group exposed to a risk factor by the incidence of the health event in a group that is not exposed. The formula for this calculation is: RR = incidence in exposed group / incidence in non-exposed group. A relative risk greater than one suggests a higher risk in the exposed group relative to the non-exposed group. Conversely, a relative risk less than one would imply a protective effect of the exposure against the health event.
In epidemiological studies such as cohort and case-control studies, relative risk helps to assess the strength of the association between exposure and health outcomes. This is often presented in the form of a "2 x 2" table to facilitate calculation. Furthermore, incidence rates are sometimes multiplied by 100 or 1,000 to convert the rates into more tangible figures, such as the number of individuals affected per 100 or 1,000 in the population.