ABSTRACT
James Johnston argued comparative studies were not done to understand principles of behavior in nature, but to see which intervention "wins." is criticisms are more applicable to some studies than others, but one should heed them when doing comparative studies. Some comparative studies are not of two different interventions but evaluate variations of the same intervention to develop and refine it. Multitreatment interference confounds direct comparisons between interventions, but in some cases multitreatment interference may be desirable. Multitreatment designs are perhaps the oldest comparative single subject experimental designs. When comparing interventions the alternating treatments design (ATD) can be used to compare two variations of the same intervention, including different parametric variations or the presence or absence of a given intervention component. A common and recommended variation of the ATD during the comparison phase is to include baseline condition observations in the alternation.
