Single‐Case Research Design and Analysis: Counseling Applications

Single-case research design (SCRD) is a type of research used to demonstrate experimental control within a single case and rigorously evaluate an intervention with one or a small number of cases (Kazdin, 2011). The single case being studied can be an individual person, a family, or a group of individuals (Morgan & Morgan, 2009). SCRDs are often known as n = 1, single-subject, small n designs, or single-case experimental designs. Gallo, Comer, and Barlow (2013) proposed that research designs that examine individuals, such as SCRDs, offer a greater understanding of the mechanisms of change in treatment. The use of a rigorous SCRD directly addresses the evidence-based question: What works for whom under what conditions? Counseling literature is replete with case studies that provide information about relationships between conditions and are helpful in understanding an individual client (Morgan & Morgan, 2009). SCRD is differentiated from case studies through its focus on the manipulation of the independent variable (i.e., counseling intervention). SCRDs are characterized by the manipulation of an independent variable--the hallmark of experimental design--and lead to causal inference that links treatment to effectiveness. Through the intensive application of repeated measures across the implementation of an intervention, SCRDs allow for the exploration of how, why, and when changes occur (Gallo et al., 2013). Experimental psychologists began studying one or a few subjects in the 1880s and continued until the early 1900s. This individualized approach succumbed to the popularity of between-group design research because of the perception of greater generalizability associated with group design and statistical analyses. However, the primary method of evaluating operant conditioning has traditionally been used by SCRD. In recent decades, SCRD experienced a resurgence in the literature, which has been attributed to the effect of the evidence-based intervention movement on applied behavioral analysis (Kazdin, 2011; Vannest, Davis, & Parker, 2013). The majority of SCRD reports are found in research on applied behavioral analysis. However, SCRD reports are still rare in professional counseling journals (Barlow, Nock, & Hersen, 2009), and this lack of SCRD studies in the counseling literature has been noted by researchers who support its use (Lenz, 2013; Sharpley, 2007). Although the rationale for the lack of SCRD publication is unclear, it is possible that counseling researchers may not be educated on its use, including the development and application of SCRD design and SCRD analysis. Because most SCRD literature is published with an emphasis on change in the overt behavior of individuals, the application of SCRD in counseling may be less evident. Counseling research typically requires the consideration of variables that are latent and less observable to the naked eye. Counseling researchers are likely to focus on the person of the client, person of the counselor, and the effect of the counseling relationship, among other variables that distinguish a counseling focus from a purely behavioral focus. The article provides an introduction to SCRD design and analysis as applied to the field of counseling. I discuss the essential features of SCRD and basic steps to conduct an SCRD study. I also address typical barriers in SCRD application. * Core Characteristics of SCRD SCRD is characterized by a specific coding system that is essential to its discussion and implementation (Riley-Tillman & Burns, 2009). A signifies the baseline condition; B is the intervention condition; C, D, and so forth denote subsequent different interventions; and when two interventions are delivered simultaneously, the lettered interventions are presented together (e.g., B-C). These conditions are often referred to as phases in SCRD. In SCRD, the participant (for counseling purposes, this would be the client) is used as his or her own control for which comparisons are made. …