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
Incidence of diarrhoea in a community can be calculated by- 
Select and explain. 
A. Case control study, B. Coho study, C. Cross sectional study, D. Double blind placebo control study
B: Coho study
Answer: B: Coho study 
Explanation: Coho study is also known as incidence study. The cohos are identified prior to the appearance of disease under investigation. The study group so defined are observed over a period of time to determine the frequency of disease among them. (refer pgno:75 park 23rd edition)