DOCUMENT RESUME ED 438 308 TM 030 619 AUTHOR Mahadevan, Lakshmi TITLE The Effect Size Statistic: Overview of Various Choices. PUB DATE 2000-01-00 NOTE 19p.; Paper presented at the Annual Meeting of the Southwest Educational Research Association (Dallas, TX, January 27-29, 2000) . PUB TYPE Reports Descriptive (141) Speeches/Meeting Papers (150) EDRS PRICE MF01/PC01 Plus Postage. DESCRIPTORS *Data Analysis; *Effect Size; Measurement Techniques; Meta Analysis; *Statistical Significance ABSTRACT Over the years, methodologists have been recommending that researchers use magnitude of effect estimates in result interpretation to highlight the distinction between statistical and practical significance (cf. R. Kirk, 1996). A magnitude of effect statistic (i.e., effect size) tells to what degree the dependent variable can be controlled, predicted, or explained by the independent variable (P. Snyder and S. Lawson, 1993). There are a number of ways one can compute an effect size statistic as part of data analysis. There is no concept of "one size fits all" (B. Thompson, 1999), so it is up to the smart researcher to choose the index best suited for a particular research endeavor. It has now become necessary that such a statistic always be included to enable other researchers to carry out meta-analyses and to inform judgment regarding the practical significance of results. This paper provides a tutorial summary of some of the effect size choices so that researchers will be able to follow the recommendations of the American Psychological Association (APA) publication manual, those of the APA Task Force on Statistical Inference, and the publication requirements of some journals. (Contains 3 tables and 11 references.) (Author/SLD) Reproductions supplied by EDRS are the best that can be made from the original document.