Small N designs for rehabilitation research

Abstract

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 technologies 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 quasiexperimental single-case designs are presented. Recommendations for designing and conducting single-case studies that contribute to the evidence base are also discussed.

Physical performance and self-report outcomes associated with use of passive, adaptive, and active prosthetic knees in persons with unilateral, transfemoral amputation: Randomized crossover trial

“…Although small samples may limit generalizability of the study findings, small samples are common in rehabilitation research [106]. This is especially true in studies related to advanced prosthetic components in which the cost of purchasing components for large numbers of participants can be prohibitive.…”

Physical Disability After Injury-Related Inpatient Rehabilitation in Children

“…To more comprehensively understand the complexities of disabling injuries in children, there has been a call for action to more robustly collect essential pediatric trauma outcomes data through multicenter research networks, 49 in addition to suggestions for useful standardized outcome measures, 50-52 rehabilitation quality of care measures, 53 and rehabilitation research design strategies. 54 …”

Opportunities in rehabilitation research

“…Often, blinding is not possible in clinical trials on technology. Although research methods exist to accommodate the challenges of small sample size, additional research is needed in the statistical methodology for alternative study designs that do not rely on large sample sizes [152]. Examples of these approaches are n of 1 studies and use of quasi-experimental designs.…”