Case studies, single-subject research, and N of 1 randomized trials: comparisons and contrasts

Am J Phys Med Rehabil. 1999 Mar-Apr;78(2):170-6. doi: 10.1097/00002060-199903000-00022.


Case studies, single-subject research designs, and N of 1 randomized clinical trials are methods of scientific inquiry applied to an individual or small group of individuals. A case study is a form of descriptive research that seeks to identify explanatory patterns for phenomena and generates hypotheses for future research. Single-subject research designs provide a quasi-experimental approach to investigating causal relationships between independent and dependent variables. They are characterized by repeated measures of an observable and clinically relevant target behavior throughout at least one pretreatment (baseline) and intervention phase. The N of 1 clinical trial is similar to the single-subject research design through its use of repeated measures over time but also borrows principles from the conduct of large, randomized controlled trials. Typically, the N of 1 trial compares a therapeutic procedure with placebo or compares two treatments by administering the two conditions in a predetermined random order. Neither the subject nor the clinician is aware of the treatment condition in any given period of time. All three approaches are relatively easy to integrate into clinical practice and are useful for documenting individualized outcomes and providing evidence in support of rehabilitation interventions.

Publication types

  • Review

MeSH terms

  • Bias
  • Double-Blind Method
  • Effect Modifier, Epidemiologic
  • Guidelines as Topic
  • Humans
  • Medical Records*
  • Randomized Controlled Trials as Topic / methods*
  • Rehabilitation
  • Reproducibility of Results
  • Research Design / standards*