ABSTRACT
This chapter describes those single case designs (SCDs) commonly referred to as “withdrawal” or “reversal” designs—one of the earliest and simplest SCDs, they involve repeating the basic baseline (A) and intervention (B) comparison by introducing and withdrawing the intervention with one or more participants. It discusses withdrawal designs' use by applied researchers investigating the effectiveness of a wide range of interventions in educational and clinical settings. The chapter also describes A-B and A-B-A designs but focuses primarily on the A-B-A-B design given its experimental utility. The A-B-A design is more useful than the basic A-B design from an experimental perspective. The A-B-A-B design provides a convincing demonstration of causality in applied research. Experimental control is demonstrated in the A-B-A-B design when the level and trend of a target behavior improves under intervention conditions and deteriorates under subsequent baseline conditions. Each replication of effect strengthens the internal validity of results.
