Percentage of Nonoverlapping Data

The Percentage of Nonoverlapping Data (PND) is a simple effect-size index for single-case research that summarizes how strongly a treatment phase departs from baseline by counting the share of treatment data points that lie beyond the most extreme baseline point. Introduced by Thomas Scruggs, Margo Mastropieri, and Glendon Casto in 1987 to allow quantitative synthesis of single-subject studies, it produces a single 0–100% number that complements visual analysis and can be aggregated across cases in a meta-analysis of single-case designs.