In research, the accessible population refers to the subset of the broader target population that the researcher can realistically reach and study, given certain practical constraints like time, location, resources, and participant availability. While the target population includes everyone who fits the criteria for a study, the accessible population is defined by who is actually available and willing to participate.
For example, if a researcher aims to study the dietary habits of all high school students in a country, the target population would be all high school students within that country. However, due to logistical limitations—such as the researcher being based in a specific region, or the study requiring participants to attend specific schools—the accessible population might be limited to high school students in that region or at certain schools that consent to participate.
Defining the accessible population is crucial for understanding the external validity of a study, or the extent to which findings can be generalized to the broader target population. If there is a significant difference between the target and accessible populations, it can limit how applicable the study’s results are to other groups. Researchers must therefore clearly delineate their accessible population, making sure readers understand its limitations and the potential impact on generalization.
In summary, the accessible population in research is the portion of the target population that the researcher can feasibly study, shaped by various logistical, ethical, and practical considerations.