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Heterogeneity (Evidence Rating Element)
Refers to the variability of the effect sizes from the different evaluation studies included in a meta-analysis (e.g., some evaluations may show strong, significant effects while other evaluations show small or no effects). This is a dimension in the Practices Scoring Instrument that rates a meta-analysis on whether the authors were aware of and attentive to heterogeneity (i.e., variability) in the effect sizes from the studies in the meta-analysis. Heterogeneity statistics include tau (t), tau-squared (t2), Q, or I-squared (I2).