Calculating Effect Size in Single-Case Research using Nonoverlap Methods

Reporting of the effect size in single subject designs that there are different ways to calculate it, has received an increased attention in recent years. The aim of this paper is to describe the calculating of effect size using non-overlap methods that are non-parametric and distribution-free and also evaluate their strengths and limitations. In a AB single subject design, 12 sessions of neurofeedback training were done for an 8-years old child who had reading disorder to determine its effectiveness in improvement of the visuospatial attention. Data was gathered using Posner Test and analyzed using PND, PAND, ECL, PEM, NAP and TAUnovlap methods. The result showed that effect sizes were obtained between 69 to 84% indicating the effectiveness of treatment in improving of visuospatial attention. This paper could be a guideline for researchers and clinicians in using non-overlap methods for calculating the effect size and deciding about the effect of treatment.