nonpopulation

Nonpopulation is a term occasionally used in statistics, demography, and survey research to denote units that do not belong to a defined population of interest. It describes the complement of a specified population frame or target group and is used to distinguish what is studied from what lies outside the study’s scope.

In practice, researchers define a target population (for example, all residents of City X in 2024). The nonpopulation comprises everyone else: residents of other areas, visitors, nonresidents, or individuals outside inclusion criteria such as age, time period, or health status.

The concept matters for sampling design and statistical estimation. It helps assess coverage bias, nonresponse, and frame errors. When reporting rates or averages, analysts must specify whether the denominator refers to the defined population or to a broader set that includes nonpopulation units. Weighting and post-stratification may be used to adjust for nonpopulation differences.

Because nonpopulation is not a universally standardized term, it is important to define it clearly in each study. Some authors avoid the term or substitute phrases like outside the population frame, out-of-scope units, or nonmembers. The term is most useful as a descriptive label rather than a formal category, and its precise meaning should be stated in methods sections to prevent misinterpretation.

See also: population, sampling frame, coverage error.