The goal of single-subject research, as with other experimental designs, is to identify cause-and-effect relationships between variables.
In common application, this means demonstrating that a treatment (variable 1) implemented or manipulated by the researcher causes a change in the participant’s responses (variable 2).
Although single-subject studies are experimental, their general methodology incorporates elements of nonexperimental case studies and time-series designs (see Chapters 13 and 10, respectively). Like a case study, single-subject research focuses on a single individual, and allows a detailed description of the observations and experiences related to that unique individual. Like time-series research, the single-subject approach typically involves a series of observations made over time.
Usually, a set of observations made before treatment is contrasted with a set of observations made during or after treatment. Although single-subject designs are similar to descriptive case studies and quasi-experimental time-series studies, the designs discussed in this chapter are capable of demonstrating cause-and-effect relationships and, therefore, are true experimental designs.