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
Cause to effect progression is seen in all except ? 
Select and explain. 
A. Case control study, B. Ecological study, C. Coho study, D. Randomized control trial
A: Case control study
Answer: A: Case control study 
Explanation: Ans. is 'a' i.e., Case control study o Case-control study proceeds backward from effect to cause, i.e. disease has already occured in subjects.o All other studies proceeds forward from cause to effect, i.e. disease has not occured in subjects.