(Effect) Size Matters: And So Does the Calculation (Report‪)‬

In 2001, the American Psychological Association (APA) noted in its publication manual that effect size calculations should be included in manuscripts submitted for publication. However, researchers utilizing single subject designs have not typically embraced the approach of any analyses beyond that of the traditional visual analysis (Marascuilo & Busk, 1988; Parsonson & Baer, 1977). In visual analysis of single subject data, researchers have examined data for three changes in the data: trend, variability, and level. Using trend analysis, researchers have examined the direction of the data for an increasing (i.e., upward) or decreasing (i.e., downward) trend. Researchers have also inspected for change in data variability or bounce. Finally, researchers have noted changes in level or mean performance.