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When Is the Difference Significant? Estimates of Meaningfulness in Clinical Research


Address correspondence to Bradley T. Conner, Temple University, Department of Psychology, Weiss Hall, 1701 N. 13th Street, Philadelphia, PA 19122. E-mail:


[Clin Psychol Sci Prac 17: 52–57, 2010]

Shearer-Underhill and Marker (2010) provide a review of effect sizes and clinical significance. They remind researchers that statistical significance and effect size estimates do not provide information that is easy for our clients to understand or use when choosing among treatment alternatives. They assert that we should be reporting more intuitive statistics, such as the number needed to treat, to convey information about clinical significance. They also present data indicating that, as a field, we are not following best practices in reporting statistical, practical, and clinical significance. The present commentary extends the discussion by providing further background information on practical and clinical significance and by making specific recommendations on how to improve our reporting of these statistics.