This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: JIPMER 2017, Subject name: Social & Preventive Medicine
In a study, group of smokers followed up for 10 years to find incidence of a cancer. What type of study design is this? 
Select and explain. 
A. Retrospective coho, B. Prospective coho, C. Case control study, D. Randomized control trials
B: Prospective coho
Answer: B: Prospective coho 
Explanation: Types of coho study: 1. Prospective/Concurrent Coho Begin in present and continue to future Outcome has not yet occurred at the time the investigation begins 2. Retrospective/Historical coho Outcomes have occurred before sta of investigation Investigator goes back in time to select study groups from existing records of past employment , up to the present 3. Ambidirectional/mixed coho Combination of retrospective and prospective coho studies