4.20 Determining if the Intervention Caused a Change in Level

Notice the importance of the baseline slope in making a prediction to inform your decision about whether the intervention caused the level to change. Even though, mathematically, the level in treatment is lower than the level in baseline, the behavior was decreasing in baseline anyway, so we would predict that the level would decrease without implementing any intervention. We are interested in whether the intervention caused the change. So, again, the treatment data are the same as what we predicted based on baseline, and it appears that this intervention did not cause a change in the slope or level of this behavior. There is no basic effect here.