Single-participant research design: Bringing science to managed care.

The ongoing transition to managed health care continues to have repercussions for health care providers, perhaps the most important of which is an emphasis on accountability for demonstrating the usefulness of clinical interventions. This requirement places a premium on intervention research and highlights the historically strained relationship between psychological research and professional practice. In the midst of this challenge, researchers have increasingly criticized the logic and practice of traditional null hypothesis significance testing. This article describes the history, epistemology, and advantages of single-participant research designs for behavioral scientists and professionals in clinical settings. Although its lack of correspondence with the Fisherian tradition has precluded widespread adoption, the single-participant alternative features a design power and flexibility well suited to both basic science and applied research.