Non-Sampling Error

What Does Non-Sampling Error Mean?
A statistical error caused by human error to which a specific statistical analysis is exposed. These errors can include, but are not limited to, data entry errors, biased questions in a questionnaire, biased processing/decision making, inappropriate analysis conclusions and false information provided by respondents.

Investopedia explains Non-Sampling Error
Non-sampling errors are part of the total error that can arise from doing a statistical analysis. The remainder of the total error arises from sampling error. Unlike sampling error, increasing the sample size will not have any effect on reducing non-sanpling error. Unfortunately, it is virtually impossible to eliminate non-sampling errors entirely.