Classifying basic research designs

Considerable confusion over terminology for classifying basic types of research design in family medicine stems from the rich variety of substantive topics studied by family medicine researchers, differences in research terminology among the disciplines that family medicine research draws from, and lack of uniform research design terminology within these disciplines themselves. Many research design textbooks themselves fail to specify the dimensions on which research designs are classified or the logic underlying the classification systems proposed. This paper describes a typology based on three dimensions that may be used to characterize the basic design qualities of any study. These dimensions are: 1) the nature of the research objective (exploratory, descriptive, or analytic); 2) the time frame under investigation (retrospective, cross-sectional, or prospective); and 3) whether the investigator intervenes in the events under study (observational or interventional). This three-dimensional typology may be helpful for teaching basic research design concepts, for contemplating research design decisions in planning a study, and as a basis for further consideration of a more detailed, uniform research design classification system.