Summarizing single-subject research. Issues and applications

In this article, literature concerning the quantitative synthesis (meta-analysis) of single subject research literature is reviewed. First, the general rationale for such an approach is discussed. Next, procedures for synthesizing single-subject literature are described, followed by comments and critiques of those procedures. Finally, a review is presented of the results of applications of those procedures. The authors suggest that procedures based on percentage of nonoverlapping data (PND) between baseline and treatment are justifiable, meaningful, and--across nine applications--have produced results that are highly meaningful and faithful to the original research reports.