ERIC Number: ED452211
Record Type: Non-Journal
Publication Date: 2001-Apr-10
Reference Count: N/A
The Efficacy of Two Improvement-over-Chance Effect Size Measures for Two-Group Univariate Comparisons under Variance Heterogeneity and Nonnormality.
Hess, Brian; Olejnik, Stephen; Huberty, Carl J.
The efficacy of two improvement-over-chance or "I" effect sizes, derived from predictive discriminant analysis (PDA) and logistic regression analysis (LRA), were investigated for two-group univariate mean comparisons. Data were generated under selected levels of population separation, variance pattern, sample size, and distribution shape. Based on the accuracy of sample estimates, both "I" indices are acceptable under optimal conditions except when both population separation and sample size are small. Under variance heterogeneity and normality, "I" derived from LRA is acceptable if "n" sizes are equal. When "n" sizes are unequal, "I" derived from LRA is acceptable only if variance heterogeneity is moderate and population separation is not small. Under nonnormality, "I" derived from LRA is acceptable regardless of the variance pattern provided "n" sizes are equal. Finally, for greater precision, "I" derived from LRA should be used under large sample sizes. Some practical implications are provided. (Contains 5 tables, 4 figures, and 43 references.) (Author/SLD)
Publication Type: Reports - Evaluative; Speeches/Meeting Papers
Education Level: N/A
Authoring Institution: N/A