<prompt> Non - sampling errors may occur due to all the following except-Inadequately calibrated instrumentsRepeated samplingObserver variationConceptual errors  <response>: 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, Parks Textbook of Preventive and Social Medicine, Page no. 913 