This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
Measure of risk calculated from case-control study is - 
Select and explain. 
A. Odds ratio, B. Relative risk, C. Attributable risk, D. Population attributable risk
A: Odds ratio
Answer: A: Odds ratio 
Explanation: It's the measure of the strength of association between risk factor and outcome The disease being investigated must be relatively rare The cases must be representative of those with the disease The controls must be representatives of those without the disease Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 81