Equal interval reduces which bias-: (A) Selection bias, (B) Berkesonian bias, (C) Interviewer bias, (D) None
Answer is A. Bias may arise due to errors of assessment of the outcome due to the human element. 3 sources: subject variation, observer bias , bias in evaluation. Selection bias: cases and controls may not be representative of cases and controls in population. There may be a systemic difference in characteristics between cases and controls. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 81