Small sample research designs for evidence-based rehabilitation: issues and methods.

Conventional research methods, including randomized controlled trials, are powerful techniques for determining the efficacy of interventions. These designs, however, have practical limitations when applied to many rehabilitation settings and research questions. Alternative methods are available that can supplement findings from traditional research designs and improve our ability to evaluate the effectiveness of treatments for individual patients. The focus on individual patients is an important element of evidenced-based rehabilitation. This article examines one such alternate approach: small-N research designs. Small-N designs usually focus on 10 or fewer participants whose behavior (outcomes) are measured repeatedly and compared over time. The advantages and limitations of various small-N designs are described and illustrated using 3 examples from the rehabilitation literature. The challenges and opportunities of applying small-N designs to enhance evidence-based rehabilitation are discussed.