ERIC Number: EJ685075
Record Type: Journal
Publication Date: 2004-Dec
Pages: 6
Abstractor: Author
ISBN: N/A
ISSN: ISSN-1082-989X
EISSN: N/A
A Note on Testing for Homogeneity Among Effect Sizes Sharing a Common Control Group
Cook, Samantha R.
Psychological Methods, v9 n4 p446-452 Dec 2004
L. V. Hedges and I. Olkin (1985) presented a statistic to test for homogeneity among correlated effect sizes and L. J. Gleser and I. Olkin (1994) presented a large-sample approximation to the covariance matrix of the correlated effect sizes. This article presents a more exact expression for this covariance matrix, assuming normally distributed data but not large samples, for the situation where effect sizes are correlated because a single control group was compared with more than one treatment group. After the correlation between effect sizes has been estimated, the standard Q statistic for correlated effect sizes can be used to test for homogeneity. This method is illustrated using results from schizophrenia research.
Descriptors: Schizophrenia, Control Groups, Effect Size, Statistical Analysis, Correlation, Psychological Studies, Research Methodology
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Publication Type: Journal Articles; Reports - Research
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A
Grant or Contract Numbers: N/A