Reporting Effect Size: The Road Less Traveled.

This paper is intended to raise awareness of the need to understand and include effect size statistics in research reports. The paper summarizes what is meant by effect size and why it is important in educational research. It then presents findings of a review of recent issues of four journals to determine the use of effect size by researchers. The paper also suggests some reasons effect size is not reported more commonly and offers some suggestions for increasing the use of such statistics. The four journals on which the review is based were chosen to provide a representative sample of educational research literature with a focus on quantitative studies. Of the 508 articles classified as quantitative or mixed method, 148 mentioned or calculated effect size, but only 82 articles included a calculation of effect size and at least limited discussion of magnitude or practical significance. Only 30 articles contained a calculated effect size and extensive discussion about effect size or magnitude. Most often, conclusions in these journals are made solely from the results of statistical inference tests. (Contains 4 tables and 36 references.) (SLD) Reproductions supplied by EDRS are the best that can be made from the original document. PERMISSION TO REPRODUCE AND DISSEMINATE THIS MATERIAL HAS BEEN GRANTED BY TO THE EDUCATIONAL RESOURCES INFORMATION CENTER (ERIC) Effect Size 1 U.S. DEPARTMENT OF EDUCATION Office of Educational Research and Improvement EDUCATIONAL RESOURCES INFORMATION CENTER (ERIC) his document has been reproduced as received from the person or organization originating it. 0 Minor changes have been made to improve reproduction quality. Points of view or opinions stated in this document do not necessarily represent official OERI position or policy. Reporting Effect Size: The Road Less Traveled James H. McMillan Sonya Lawson Kristi Lewis Angela Snyder Virginia Commonwealth University Paper presented at the 2002 Annual Meeting of the American Educational Research Association, April 5, New Orleans. 2 IEN COPY AVAILABLE