Abstract: The growing emphasis on evidence-based practice places a premium on the development of high quality academic and social behavior interventions. Likewise, there is increasing pressure to be accountable for the services provided to students, highlighting the importance of monitoring the effectiveness of interventions employed. As the importance of intervention outcome data increases, it is essential not only to document whether academic or social behavior changes have occurred but also if the intervention in question was responsible for those substantiated changes. This is best accomplished by employing a defensible intervention methodology within the framework of a single subject research design. This article examines the basis of the experimental reasoning behind single subject methodology (i.e., baseline logic) as well as the importance of using defensible intervention methodologies in the context of response-to-intervention models. Four designs are reviewed that have direct