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
The purpose of double blinding in clinical trials is to? 
Select and explain. 
A. Achieve comparability between study and control groups, B. Avoid observer bias, C. Avoid subject bias, D. Avoid observer and subject bias
D: Avoid observer and subject bias
Answer: D: Avoid observer and subject bias 
Explanation: Ans. is 'd' i.e., Avoid observer and subject bias Double blinding ensures that both the observer and subject are unaware of the group allocation and treatment. It there by eliminates both subject bias and the observer bias.