Ans. C. ARR = 1% and RR = 0.9(Ref. Park 24/e p83)In the given situation, absolute risk reduction (ARR) is 1% and relative risk (RR) is 0.9.Relative Risk (RR)Attributable Risk (AR)Population Attributable Risk (PAR)RR=IExp/INon-Exp AR=(IExp-INon-Exp)/INon-ExpX100 AR=(Total-INon-exp)/ITotalX100RR is the ratio of the risk in the exposed divided by the risk in the unexposed.AR indicates the number of cases of a disease among exposed individuals that can be attributed to that exposureIt is excess risk or risk differenceUseful measure of extent of public health problem caused by an exposure PAR indicates the number (or propoion) of cases that would not occur in a population if the factor were eliminated. Control group (old drug)Intervention group (New drug)Developed HT complications18001620Did not develop HT complications1342513605Total subjects1522515225IC = Incidence of events (hypeensive complications) in the control group = 1800/15225 = 0.118 = 11.8%IT = Incidence of events (hypeensive complications) in the treatment group = 1620/15225 = 0.106 = 10.6%Absolute risk reduction (ARR) is also known as risk difference.ARR = IC-IT = 11.8 -10.6 = 1.2%Relative risk (RR) = IT/IC = 0.106/0.118 = 0.9