Target Population

The target population for a survey is the entire set of units for which the survey data are to be used to make inferences. Thus, the target population defines those units for which the findings of the survey are meant to generalize. Establishing study objectives is the first step in designing a survey. Defining the target population should be the second step.

Target populations must be specifically defined, as the definition determines whether sampled cases are eligible or ineligible for the survey. The geographic and temporal characteristics of the target population need to be delineated, as well as types of units being included. In some instances, the target population is restricted to exclude population members that are difficult or impossible to interview. For instance, area household surveys tend to define their target populations in terms of the civilian, noninstitutionalized population of the United States. Any exclusion made to the target population must also be reflected in the inferences made using the data and the associated presentations of findings. Undercoverage of the target population occurs when some population units are not linked or associated with the sampling frame and hence have no chance of inclusion in the survey. The subset of the target population that has a chance of survey inclusion because of their membership in, or linkage to, the sampling frame is referred to as the survey population. Traditional telephone surveys have a survey population of households with landline telephone service but typically are used to make inferences to target populations of all households, regardless of telephone service. In some instances, surveys have more than one target population because analysis is planned at multiple levels. For instance, a health care practices survey might have a target population defined in terms of households, another defined in terms of adults, and another defined in terms of children. Such a survey might sample households, collect household-level data, and then sample an adult and a child for interviews at those levels.

For business surveys, the target population definition must also specify the level of the business that comprises the units of the target population. Surveys of business finances typically define their target populations in terms of the enterprise—the organizational level that has ownership and ultimate responsibility [Page 876]for making decisions for the entire business. Labor force surveys define their target populations in terms of the establishment, that is, at the organizational level, where employment activities are conducted at or from a particular geographic location.