In a study 400 smokers and 600 non-smokers were followed up over a period oflO years to find out the incidence of hypertension. The following table summarizes the data at the end of the study: Hypertension YesNoTotalSmokingYes120280400 No30570600 Total1508501000Calculate the risk ratio in this study is:

Answer: C. 6. (Ref Park's Textbook of PSM 22nd/Pg.75)# Incidence in exposed (smoker) is = 120/400= 0.3# Incidence in non exposed (non-smoker) = 30/600= 0.05# Risk ratio (Relative Risk) = Incidence in exposed/ Incidence in non exposed = 0.3/0.05 = 6# RR is direct measure of strength of association. RR=1 means no association. RR > 1 means positive association.