This chapter also discussed the complex issues surrounding causality, the various alternative explanations that may be given for any evaluation outcome, and the issues regarding generalization of...

This chapter also discussed the complex issues surrounding causality, the various alternative explanations that may be given for any evaluation outcome, and the issues regarding generalization of outcomes. Some single-system designs are stronger than others in reducing alternative explanations. We concluded the chapter with an overview of single-system designs. However, we want to emphasize that the designs presented are basically “ideal types” that are described to help you understand the variety of uses and conclusions that are available from single-system designs. In real practice, you may use some of these designs exactly as described, or variations of them that specifically fit the needs of a particular case. Essentially, all single-system designs begin with recording and then simply reflecting the changes you make in your interventions in subsequent phases. This is in line with our emphasis in this book that practice guides evaluation, rather than the other way around.