Types of Sampling in Social Research

The value and credibility of research results depend greatly on how the subjects or participants are selected. Nevertheless, the sampling process is often superficially described in many research reports and articles, and the chosen sampling procedure is rarely justified by researchers. One possible cause of this situation may be the inconsistencies present in the methodological literature regarding this stage of research. In an attempt to provide clarification, I propose a classification of sampling methods that can be used in studies involving multiple units of investigation, using the criterion of representativeness. Probability sampling and theoretical sampling are representative; they allow for internal generalization of results through statistical induction and analytical induction respectively. All other types of sampling described in the specialized literature are unrepresentative. For these latter types to be acceptable in scientific research, they must be systematic, controlled, and show a concern for increasing representativeness by reducing subjectivity in the process of selecting subjects / participants in the study. Applying these acceptability criteria forces greater transparency in the sampling procedures used and allows for more accurate evaluation of the research results.