An ABAB research design, also called a withdrawal or reversal design, is used to determine if an intervention is effective in changing the behavior of a participant. The design has four phases denoted by A1, B1, A2, and B2. In each phase, repeated measurements of the participant’s behavior are obtained. Hence, the participant serves as his or her own control. The first phase, A1, is used to establish a baseline for the behavior. The intervention phase, B1, is introduced after a stable baseline has been established. In the third phase, A2, the intervention is withdrawn, and the baseline condition is reinstated. After baseline stability has been reestablished, the intervention is presented a second time, the B2 phase. Baseline measurements are taken until they stabilize at ...