(Effect) Size Matters: And So Does the Calculation

The purpose of this paper is to present the types of measures that may be used to describe intervention effects from single subject designs. A regression approach and several non-regression approaches are described. Non-regression approaches include Standard Mean Difference, Percentage of Non-Overlapping Data, Percent Reduction, and Percentage Exceeding the Median. Researchers are encouraged to combine a non-regression measure along with considerations of methodological rigor and visual analysis to fully appreciate the contributions of single subject intervention data.