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
In a case-control study, all can be measured except 
Select and explain. 
A. Relative risk, B. Incidence, C. Odds ratio, D. Cause & effect relation
A: Relative risk
Answer: A: Relative risk 
Explanation: Relative risk=incidence among exposed/incidence among non exposed A typical case-control study does not provide incidence rates from which relative risk can be calculated directly because there is no appropriate denominator or population at risk to calculate these rates. In general, relative risk can be exactly determined only from a coho study. (pg no:73 park 23 rd edition )