Scruggs, Mastropieri, & Casto (1987) proposed the percentage of non-overlapping data (PND) as an effect size index for single-case designs. For an outcome where increase is desirable, PND is defined as the proportion of observations in the B phase that exceed the highest observation from the A phase. For an outcome where decrease is desirable, PND is the proportion of observations in the B phase that are less than the lowest observation from the A phase.
For an outcome where increase (decrease) is desirable, Parker et al. (2011a) defined PAND as the proportion of observations remaining after removing the fewest possible number of observations from either phase so that the highest remaining point from the baseline phase is less than the lowest remaining point from the treatment phase (lowest remaining point from the baseline phase is larger than the highest remaining point from the treatment phase).
This effect size does not have a stable parameter definition because its magnitude depends on the number of observations in each phase (Pustejovsky, 2019).