ABSTRACT
This chapter presents a case for combining single case research designs (SCRD) when the research question or circumstances call for it. SCRDs are combined when planning a study, or attempting to salvage experimental control during a study in progress. Combination designs, while sometimes difficult to implement, may assist researchers in controlling for threats to internal validity. M. Sidman described a research design that Hall named the changing criterion design. This design may be appropriate for teachers, clinicians, and other applied researchers who wish to evaluate instructional or therapy programs that require gradual, stepwise changes in behavior. The strength of the changing criterion design is in its demonstration of a close correspondence between criterion-level change and behavior change that is data fall within a pre-established range at each criterion level. The changing criterion design is one of several experimental paradigms available to educators and clinicians to evaluate the effectiveness of intervention programs.
