Coba jelasin Nonrepresentative samples dari Jajal pamanggih dalam bahasa sunda dong

Another source of error is the deliberate or accidental use of nonrepresentative samples. For example, when home telephones were rare, telephone sampling had a built-in error because most of those surveyed were well-to-do.

Péople asked to participate in opinion polls also have the right to refuse; this méans that the sample is self-selected and consequently a non-probability sample. The validity of the results and of the statistical techniques used to derive characteristics of the sample such as the margin of error are therefore highly questionable.