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
Cause to effect progression is seen in all EXPECT: 
Select and explain. 
A. Case control study, B. Ecological study, C. Coho study, D. Randomized control trail
A: Case control study
Answer: A: Case control study 
Explanation: Case control studies aare called retrospective studies. Both exposure and outcome has already occured. The study proceeds backwards from effect to cause It uses control or comparison group to suppo or refute an inference. Parks textbook of preventive and social medicine.K Park. Edition 23.Pg no: 71