Best research evidence for physical medicine and rehabilitation.

Evidence-based medicine is a strong movement in this century, and randomized clinical trials continue to be the best level of evidence for establishing cause-effect relationships between treatment interventions and outcomes. The field of physical medicine and rehabilitation has many excellent research questions on the effects of treatment but seems to rely mostly on weak observational methods (eg, chart review, case series, and single-group designs) for answers. This paper highlights 3 basic and relatively simple principles of good experimental design: control, randomization, and replication that were developed by R. A. Fisher for large, complex, agricultural field trials. The principles diffused readily into many scientific arenas, and Fisher even applied the principles in his backyard studies into Mendelian genetics. The thoughts of R. A. Fisher, arguably the most influential statistician of the 20th century, on the promise and challenges of randomized clinical trials in medicine should motivate rehabilitation clinicians to do their own small-scale controlled trials, with Institutional Review Board approval, when faced with equally realistic and plausible treatment options for their patients.