Compare methods

	Standardized Effect Size for Single-Case Research	Single-System Design
Field	Social Work	Social Work
Family	Process / pipeline	Process / pipeline
Year of origin	2012	2009
Originator	Larry V. Hedges, James E. Pustejovsky & William R. Shadish	Martin Bloom, Joel Fischer & John G. Orme (codification in social work)
Type	Standardized mean-difference effect size comparable to between-groups d	Time-series design for evaluating intervention with a single client system
Seminal source	Hedges, L. V., Pustejovsky, J. E., & Shadish, W. R. (2012). A standardized mean difference effect size for single case designs. Research Synthesis Methods, 3(3), 224–239.	Bloom, M., Fischer, J., & Orme, J. G. (2009). Evaluating Practice: Guidelines for the Accountable Professional (6th ed.). Pearson/Allyn & Bacon. ISBN: 9780205458066
Aliases	Single-Case d, Within-Case Standardized Mean Difference, Design-Comparable Effect Size, Single-Case Standardized Mean Difference	Single-Subject Design, Single-Case Design, N-of-1 Design, Single-System Evaluation
Related	3	4
Summary	A standardized effect size for single-case research expresses the difference between treatment and baseline phases in standard-deviation units so that it can be placed on the same scale as the familiar between-groups Cohen's d and combined across studies in a meta-analysis. The design-comparable estimator of Hedges, Pustejovsky, and Shadish (2012) explicitly models within-case and between-case variation and applies a small-sample correction, addressing the long-standing problem that nonoverlap indices and naive single-case d statistics are not comparable to the effect sizes used in group-design research.	A single-system design is a time-series approach to evaluating practice in which a single client system — an individual, family, group, or organization — is measured repeatedly on a clearly defined target before and during (and sometimes after) an intervention. By tracking the same system over time rather than comparing a treatment group to a control group, it lets a practitioner judge whether their own intervention is associated with change in the people they actually serve. It is the methodological backbone of the 'accountable professional' tradition codified by Bloom, Fischer, and Orme.