This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Analytical Epidemiology, Subject name: Social & Preventive Medicine
'Confounding bias' in a case control study can be removed by: 
Select and explain. 
A. Double blinding, B. By properly recalling events, C. Matching, D. By selecting representative population
C: Matching
Answer: C: Matching 
Explanation: Ans; C (Matching) Ref: Park 22nd editionExplanation:Confounder is a variable which is an independent risk factor for disease and is non- causal.ly associated with the exposure.That is the variable should be related to the disease and to the risk factor under study like shown in the following figure: To remove the effect of confounding at the design-stage, matching is done, i.e., cases and controls are similar with respect to confounding variable.