Assessing Heterogeneity in Meta-Analysis: Q Statistic or I 2 Index?

In meta-analysis, the usual way of assessing whether a set of single studies is homogeneous is by means of the Q test. However, the Q test only informs meta-analysts about the presence versus the absence of heterogeneity, but it does not report on the extent of such heterogeneity. Recently, the I 2...

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Bibliographic Details
Published in:Psychological methods 2006-06, Vol.11 (2), p.193-206
Main Authors: Huedo-Medina, Tania B, Sánchez-Meca, Julio, Marín-Martínez, Fulgencio, Botella, Juan
Format: Article
Language:English
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Summary:In meta-analysis, the usual way of assessing whether a set of single studies is homogeneous is by means of the Q test. However, the Q test only informs meta-analysts about the presence versus the absence of heterogeneity, but it does not report on the extent of such heterogeneity. Recently, the I 2 index has been proposed to quantify the degree of heterogeneity in a meta-analysis. In this article, the performances of the Q test and the confidence interval around the I 2 index are compared by means of a Monte Carlo simulation. The results show the utility of the I 2 index as a complement to the Q test, although it has the same problems of power with a small number of studies.
ISSN:1082-989X
1939-1463
DOI:10.1037/1082-989X.11.2.193