Flexibility of single-subject experimental designs. Part III: Using flexibility to design or modify experiments.

The purpose of this paper is to present clinical researchers with viable alternatives to basic, prototypical single-subject experimental designs. The availability of these alternatives is a product of the flexibility inherent in the application of these designs. Two general types of flexibility are discussed: a priori flexibility, as in combining designs in one study and ad hoc flexibility in which a design is modified during the course of a study. The flexibility afforded by the designs provides the opportunity to fashion individual experimental designs for specific research problems addressed. A review of the clinical research literature published during the last 10 years revealed that the flexibility of these designs has been underutilized. The benefits that can derive from using the potential flexibility of the designs are described, and specific suggestions are made for incorporating flexibility into clinical research.