Ratio of incidence among exposed and non exposed is known as -

Ans. is 'a' i.e., Risk ratio 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.RR =Incidence of disease among exposedIncidence 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).