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
Problem of bias is maximum with 
Select and explain. 
A. Coho study, B. Case study, C. Case control study, D. Experimental study
C: Case control study
Answer: C: Case control study 
Explanation: Bias is any systemic error in the determination of the association between exposure and disease. The relative risk may increase or decrease as a result of the bias it reflects some type of no compatibility between the study and control groups. The possibility of bias must be considered when evaluating a possible cause and effect relationship. (refer pgno 73, park 23rd edition)