Non - sampling errors may occur due to all the following except-: (A) Inadequately calibrated instruments, (B) Repeated sampling, (C) Observer variation, (D) Conceptual errors
Answer is B. Errors may occur not only due to error in sample survey but also due to inadequately calibrated instruments, observer variation, incomplete coverage, and conceptual errors. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 913