Flexibility of single-subject experimental designs. Part II: Design selection and arrangement of experimental phases.

The purpose of this paper is to present a taxonomy of single-subject experimental designs and discuss relevant examples that underscore the versatility and flexibility of this approach to clinical research. The proposed taxonomy serves as a heuristic model that may facilitate an understanding of single-subject experimental designs. Four general evaluation strategies employed in applied research--treatment-no treatment comparison, component assessment, treatment-treatment comparison, and successive level analysis--are discussed within this schema. Each of these evaluation strategies is related to commonly posed clinical research questions, and published examples of design options that address these questions are presented. Throughout the discussion basic considerations relating to appropriate design selection are reviewed.