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Wilcox, Rand R.3
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Wilcox, Rand R. – Educational and Psychological Measurement, 2005
It is known that nonnormality, a heteroscedastic error term, or a nonlinear association can create serious practical problems when using the conventional analysis of covariance (ANCOVA) method. This article describes a simple ANCOVA method that allows heteroscedasticity, nonnormality, nonlinearity, and multiple covariates. When standard…
Descriptors: Statistical Analysis, Error of Measurement, Measurement Techniques
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Wilcox, Rand R. – Educational and Psychological Measurement, 1997
Some results on how the Alexander-Govern heteroscedastic analysis of variance (ANOVA) procedure (R. Alexander and D. Govern, 1994) performs under nonnormality are presented. This method can provide poor control of Type I errors in some cases, and in some situations power decreases as differences among the means get large. (SLD)
Descriptors: Analysis of Variance, Error of Measurement, Power (Statistics), Statistical Distributions
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Wilcox, Rand R. – Educational and Psychological Measurement, 1980
Using three sets of real data, a comparison of four discrete discriminate analysis procedures is made using the actual versus the optimal error rate. The kernel method gives the most accurate results in all three cases. (Author/RL)
Descriptors: Achievement Tests, Comparative Analysis, Discriminant Analysis, Error of Measurement