10.1177/001316402236877 EDUCATIONAL AND PSYCHOLOGICAL MEASUREMENT CAPRARO AND CAPRARO TREATMENTS OF EFFECT SIZES AND STATISTICAL SIGNIFICANCE TESTS IN TEXTBOOKS ROBERT M. CAPRARO AND MARY MARGARET CAPRARO Texas A&M University The dialog surrounding effect sizes and statistical significance tests often places the two ideas into separate camps amid controversy. In light of recommendations by the Task Force on Statistical Inference and the fifth edition of the American Psychological Asso- ciation Publication Manual calling for the reporting of effect sizes, a review of treat- ments of effect sizes in textbooks may be quite timely. This study reviews textbooks published since 1995 and as regards treatments of effect sizes and statistical significance tests. Of the textbooks examined, every textbook (n = 89) included the topic of statistical significance testing (2,248 pages), whereas only a little more than two thirds of the text- books (n = 60) included information on effect sizes (789 pages). The controversy regarding statistical significance testing and effect size reporting as discussed in the literature is rendered moot with the current edi- tion of the American Psychological Association (APA) PublicationManual (2001) (cf. Daniel, 1998; Ernest & McLean, 1998; Fan, 2001; Henson & Smith, 2000; Mittag & Thompson, 2000; Nix & Barnette, 1998). Statistical significance testing will continue, but effect size reporting will become prev- alent as journal editors revise editorial policies to reflect recommendations of the APA (2001). Reflecting the movement of the field, the editorial policies at 20 journals now formally “require” effect size reporting (cf. McLean & Kaufman, 2000; Murphy, 1997; Snyder, 2000), including 2 journals circulated to more than 50,000 persons (i.e., the flagship journals of the American Counseling Asso- Correspondence to the first and second authors should be sent to rcapraro@coe.tamu.edu and mmcapraro@coe.tamu.edu, respectively. Educational and Psychological Measurement, Vol. 62 No. 5, October 2002 771-782 DOI: 10.1177/001316402236877 © 2002 Sage Publications 771