Improving Research Clarity and Usefulness with Effect Size Indices as Supplements to Statistical Significance Tests

Abstract

Articles published in professional journals are expected to comply with the 1994 publication manual of the American Psychological Association, which acknowledges that p values are not acceptable measures of effect size magnitudes, and explicitly encourages authors to report effect sizes. This “encouragement” is also consistent with recent criticisms of common misuses of statistical significance tests. The present article examined effect size reporting in 23 quantitative articles reported in Exceptional Children. It was found that effect sizes are rarely being reported, though exemplary reporting practices were also noted Reasons why the APA “encouragement” has been ineffective are explored and it is suggested that an editorial policy requiring effect size reporting similar to that invoked at several journals, including some APA journals, may be useful.