Journal of Rehabilitation Research & Development (JRRD)

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Volume 49 Number 1, 2012
   Pages 175 — 186

Abstract — Small N designs for rehabilitation research

Scott D. Barnett, PhD;1* Allen W. Heinemann, PhD;2 Alexander Libin, PhD;3 Arthur C. Houts, PhD;4 Julie Gassaway, MS, RN;5 Sunil Sen-Gupta, PhD, MPH;6 Aaron Resch, MS;7 Daniel F. Brossart, PhD7
1Center of Excellence: Maximizing Rehabilitation Outcomes, James A. Haley Veterans Hospital, Tampa, FL; 2Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, ??Chicago, IL; 3Georgetown University Medical Center, Department of Rehabilitation Medicine, Washington, DC; 4University of Memphis, Professor Emeritus, Memphis, TN; 5Institute for Clinical Outcomes Research, Salt Lake City, UT; 6Department of Veterans Affairs, Rehabilitation Research and Development Service, Washington, DC; 7Department of Educational Psychology, Texas A&M University, College Station, TX

Abstract — Rehabilitation research presents unique and challenging problems to investigators during both the design and analysis periods. Statistical issues regarding sample size requirements for an adequately powered study may be in direct conflict with realistic recruitment and subject retention goals. Issues of underpowered studies, sample size requirements, and recruitment goals plague rehabilitation research. Randomized clinical trials (RCTs) are typically narrow in scope and thus lack generalizability to everyday, yet specific, clinical problems; they are also costly and time-consuming and require large numbers of participants for randomization to have optimal, desired effects. Further, the RCT design may not be applicable to assistive tech nologies and environmental modifications–vital components of disability and rehabilitation research–nor is it appropriate in situations in which theoretical models of change are lacking or premature. Single-case designs are better suited for studies in which understanding and changing patient behavior and functional status are primary goals and the targeted sample sizes are less than 30 and frequently less than 10. Theoretical, methodological, and clinical reasons for using experimental and quasi-experimental single-case designs are presented. Recommendations for designing and conducting single-case studies that contribute to the evidence base are also discussed.

Key words: case reports, case series, experimental design, randomized clinical trial, rehabilitation, research design, single-case study, single-subject design, small N, statistics.

View HTML  ¦  View PDF  ¦  Contents Vol. 49, No. 1
This article and any supplementary material should be cited as follows: Barnett SD, Heinemann AW, Libin A, Houts AC, Gassaway J, Sen-Gupta S, Resch A, Brossart DF. Small N designs for rehabilitation research. J Rehabil Res Dev. 2012;49(1):175–86.
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