This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
Cross-product ratio is estimated by ? 
Select and explain. 
A. Coho study, B. Case-control study, C. Cross sectional study, D. Field trial
B: Case-control study
Answer: B: Case-control study 
Explanation: Ans. is 'b' i.e., Case-control studyOdds - ratio (cross product ratio)From a case control study odds ratio can be derived which a measure of the strength of association between risk factor and outcome.Odds ratio is closely related to relative risk (which is analysed in coho study) 4 odds ratio represents only an estimate of relative risk.