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
[{'content': 'Relative risk is associated with: September 2007 \nSelect and explain. \nA. Coho studies, B. Cross sectional studies, C. Envoirnmental studies, D. Case control studies', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A: Coho studies The relative risk (RR), also called risk ratio, is simply a ratio of the probability of the disease occurring in an exposed group versus a non-exposed group. This measure of effect size differs from the odds ratio in that it compares probabilities instead of odds, but asymptotically approaches the latter for small probabilities. While both measures are useful, they have different statistical uses. In medical research, for example, the odds ratio is oured for case-control studies and retrospective studies. Relative risk is used in randomized controlled trials and coho studies.', 'role': 'assistant'}]