Compare methods

	Nonoverlap of All Pairs	Single-System Design
Field	Social Work	Social Work
Family	Process / pipeline	Process / pipeline
Year of origin	2009	2009
Originator	Richard I. Parker & Kimberly J. Vannest	Martin Bloom, Joel Fischer & John G. Orme (codification in social work)
Type	All-pairs nonoverlap effect size for single-case designs	Time-series design for evaluating intervention with a single client system
Seminal source	Parker, R. I., & Vannest, K. J. (2009). An improved effect size for single-case research: Nonoverlap of all pairs. Behavior Therapy, 40(4), 357–367.	Bloom, M., Fischer, J., & Orme, J. G. (2009). Evaluating Practice: Guidelines for the Accountable Professional (6th ed.). Pearson/Allyn & Bacon. ISBN: 9780205458066
Aliases	NAP, Nonoverlap of All Pairs (NAP), Parker-Vannest NAP, All-Pairs Nonoverlap	Single-Subject Design, Single-Case Design, N-of-1 Design, Single-System Evaluation
Related	4	4
Summary	Nonoverlap of All Pairs (NAP) is an effect-size index for single-case research that measures how completely a treatment phase separates from a baseline phase by examining every possible pairing of a baseline point with a treatment point. Introduced by Richard Parker and Kimberly Vannest in 2009 as an improvement on the Percentage of Nonoverlapping Data, NAP reports the proportion of those pairs in which the treatment point shows improvement, is mathematically equivalent to the area under a ROC curve and the Mann-Whitney statistic, and therefore carries a known sampling distribution that supports confidence intervals and significance testing.	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.