Quantifying heterogeneity in a meta-analysis.

@article{Higgins2002QuantifyingHI,
  title={Quantifying heterogeneity in a meta-analysis.},
  author={Julian P. T. Higgins and Simon G Thompson},
  journal={Statistics in medicine},
  year={2002},
  volume={21 11},
  pages={
          1539-58
        }
}
The extent of heterogeneity in a meta-analysis partly determines the difficulty in drawing overall conclusions. This extent may be measured by estimating a between-study variance, but interpretation is then specific to a particular treatment effect metric. A test for the existence of heterogeneity exists, but depends on the number of studies in the meta-analysis. We develop measures of the impact of heterogeneity on a meta-analysis, from mathematical criteria, that are independent of the number… 
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