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A d-statistic for single-case designs that is equivalent to the usual between-groups d-statistic
William R Shadish1, Larry V Hedges, James E Pustejovsky
1a School of Social Sciences, Humanities and Arts , University of California , Merced , CA , USA.
Neuropsychological Rehabilitation
|July 19, 2013
Summary
A new standardized mean difference statistic (d) for single-case designs allows for summarizing treatment effects, conducting power analyses, and performing meta-analyses across studies. This statistically robust measure enhances research in single-case experimental designs.
Area of Science:
- Psychology
- Statistics
- Research Methodology
Background:
- Single-case designs are crucial for evaluating interventions in various fields.
- Existing effect size measures for single-case designs have statistical limitations.
- Standardized effect sizes are needed for robust meta-analysis and research synthesis.
Purpose of the Study:
- To introduce a standardized mean difference statistic (d) for single-case designs.
- To demonstrate its utility in summarizing effects within and across studies.
- To provide tools for power analysis and meta-analysis in single-case research.
Main Methods:
- Development of a standardized mean difference statistic (d) analogous to between-groups designs.
- Application of the d-statistic for summarizing effects across multiple cases.
- Utilizing the d-statistic for power calculations in study planning.
- Integration of the d-statistic for meta-analytic synthesis of single-case studies.
- Discussion of limitations and potential remedies for the d-statistic.
Main Results:
- The proposed d-statistic is statistically equivalent to the standard d in between-groups experiments.
- The d-statistic effectively summarizes treatment effects across cases within a study.
- The d-statistic facilitates power analyses for planning new single-case studies.
- The d-statistic enables meta-analysis of effects across studies with different outcome measures.
- SPSS macros are available for effect size computation and power analysis.
Conclusions:
- The new d-statistic offers a statistically sound and versatile measure for single-case designs.
- This standardized effect size facilitates research synthesis and meta-analysis.
- The availability of SPSS macros supports the practical application of this method in research and grant proposals.
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