This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiological Study, Subject name: Social & Preventive Medicine
[{'content': "In a study done to establish Smoking as a risk factor for a disease, 30 out of 50 smokers developed the disease while 10 out of 50 non-smokers developed the disease. Odd's ratio is? \nSelect and explain. \nA. 3, B. 6, C. 5, D. 10", 'role': 'user'}, {'content': 'Answer: B \nExplanation: ANSWER: (B) 6REF: Park 20th edition page 69 SmokerNon smoker Disease301040Non disease204060 5050 Odds ratio = (30 x 40)/ (20 x 10)= 6', 'role': 'assistant'}]