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Assessing heterogeneity in meta-analysis: Q statistic or I2 index?
Tania B Huedo-Medina1, Julio Sánchez-Meca, Fulgencio Marín-Martínez
1Department of Basic Psychology & Methodology, University of Murcia, Murcia, Spain. hmtania@um.es
Psychological Methods
|June 21, 2006
Summary
The Q test indicates heterogeneity presence but not extent. The I(2) index quantifies this extent, complementing the Q test in meta-analysis, though both have power issues with few studies.
Area of Science:
- Biostatistics
- Medical Research Methodology
Background:
- The Q test is standard for assessing statistical heterogeneity in meta-analysis.
- The Q test only indicates the presence or absence of heterogeneity, not its magnitude.
Purpose of the Study:
- To compare the performance of the Q test and the I(2) index for quantifying heterogeneity in meta-analysis.
- To evaluate the utility of the I(2) index confidence interval.
Main Methods:
- A Monte Carlo simulation was employed to compare the Q test and the I(2) index.
- Performance was assessed based on their ability to quantify heterogeneity.
Main Results:
- The I(2) index effectively quantifies the degree of heterogeneity, serving as a valuable complement to the Q test.
- Both the Q test and the I(2) index exhibit limitations in statistical power when analyzing a small number of studies.
Conclusions:
- The I(2) index is a useful tool for assessing the extent of heterogeneity in meta-analyses.
- Researchers should consider the I(2) index alongside the Q test, being mindful of sample size limitations.
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