Educational stakeholders are keen to know the magnitude and importance of different interventions. However, the way evidence is communicated to support understanding of the effectiveness of an intervention is controversial. Typically studies in education have used the standardised mean difference as a measure of the impact of interventions. This…

The Institute of Education Sciences has funded more than 100 experiments to evaluate educational interventions in an effort to generate scientific evidence of program effectiveness on which to base education policy and practice. In general, these studies are designed with the goal of having adequate statistical power to detect the average…

Presents use of the effect size as a descriptive statistic for single-subject research. Discusses the way in which effect sizes augment interpretation of results, and reviews four types of treatment effects with case studies. An appendix includes a sample computer program for computing effect sizes. (SLD)