Relative risk is represented by -

Ans. is 'a' i.e., Incidence among exposed/incidence among nonexposed Relative risk (risk ratio)o Relative risk is the ratio of the incidence of the disease (or death) among exposed and the incidence among nonexposed.Incidence of disease amone exposedRR =----------------------------------------------------------------Incidence of disease among nonexposedo RR is a direct measure of the strength of the association between the suspected cause and effect,o A relative risk of one indicates no association.o A relative risk greater than one indicates positive association between the exposure and the disease under study,o For example, a RR of 2 indicates that the incidence rate of disease is 2 times higher in exposed group as compared with unexposed - 100% increase in risk.o A relative risk of less than one indicates negative association^ i.e. exposure to a factor will decrease the incidence of disease (e.g. exposure to vit A decreases the incidence of skin cancer).