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ERIC Number: EJ933704
Record Type: Journal
Publication Date: 2011-Jun
Pages: 6
Abstractor: As Provided
Reference Count: 22
ISSN: ISSN-1531-7714
First among Others? Cohen's "d" vs. Alternative Standardized Mean Group Difference Measures
Cahan, Sorel; Gamliel, Eyal
Practical Assessment, Research & Evaluation, v16 n10 Jun 2011
Standardized effect size measures typically employed in behavioral and social sciences research in the multi-group case (e.g., [eta][superscript 2], f[superscript 2]) evaluate between-group variability in terms of either total or within-group variability, such as variance or standard deviation--that is, measures of dispersion about the mean. In contrast, the definition of Cohen's "d", the effect size measure typically computed in the two-group case, is incongruent due to a conceptual difference between the numerator--which measures between-group variability by the intuitive and straightforward raw difference between the two group means--and the denominator--which measures within-group variability in terms of the difference between all observations and the group mean (i.e., the pooled within-groups standard deviation, S[subscript W]). Two congruent alternatives to "d", in which the root square or absolute mean difference between all observation pairs is substituted for S[subscript W] as the variability measure in the denominator of "d", are suggested and their conceptual and statistical advantages and disadvantages are discussed. (Contains 3 footnotes.)
Dr. Lawrence M. Rudner. e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A