This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
Relative risk can be obtained from 
Select and explain. 
A. Case study, B. Coho study, C. Case control study, D. Experimental study
B: Coho study
Answer: B: Coho study 
Explanation: Strength of association in Coho study Strength of associationFormulaRelative risk (Risk ratio)RR = Incidence among exposed Incidence among non exposed RR > 1Positive association RR = 1 No association RR < 1Negative association Attributable riskAR = Incidence among exposed-Incidence among non exposedIncidence among exposed x 100Population attributable risk PAR = = Incidence among total -Incidence among non exposedIncidence among total x 100(Refer: K. Park's Textbook of Preventive and Social Medicine, 24th edition, pg no: 83, 93)