Meta-analysis of variation: ecological and evolutionary applications and beyond
Meta-analysis of variation: ecological and evolutionary applications and beyond
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DOI：
10.1111/2041-210x.12309
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发表时间：
2015-02-01
影响因子：
6.6
通讯作者：
Senior, Alistair M.
中科院分区：
文献类型：
--
作者：
Nakagawa, Shinichi;Poulin, Robert;Senior, Alistair M.
1. 荟萃分析已成为许多领域（包括生态学和进化论）总结实证研究的标准方法。在生态学和进化论中，比较两组（通常是实验组和对照组）的荟萃分析几乎完全集中于使用标准化指标（例如 Cohen's / Hedges'd 或响应比）来比较方法。2．然而，实验处理不仅会影响平均值，还会影响方差。研究两组之间方差的差异可能会提供丰富的信息，特别是当治疗影响方差而不是平均值时。3。在本文中，我们提出了效应大小统计 lnCVR（两组变异系数 CV 之比的自然对数），这使我们能够通过荟萃分析比较两组变异性之间的差异。我们用生态学和进化论的例子来说明lnCVR的使用。4．此外，作为使用 lnCVR 的替代方法，我们建议在分层（线性混合）模型中结合使用 ln s（对数标准差）和 ln x（对数平均值）。使用 ln s 与 ln x ="false" 克服了 lnCVR 的潜在限制，并且它提供了一种更灵活、尽管更复杂的方法来检查两组比较之外的变异。相关地，我们还参考了 ln s 和 lnCV（log CV）在比较分析中的潜在用途。5。我们比较变异性的方法可以应用于已经发布的荟萃分析数据集，这些数据集比较两组均值，以发现可能被忽视的方差影响。此外，我们的方法应该应用于未来的荟萃分析，特别是当人们怀疑一种治疗方法不仅对平均值有影响，而且对方差也有影响时。值得注意的是，所提出的方法的应用超出了生态学和进化领域。
1. Meta-analysis has become a standard way of summarizing empirical studies in many fields, including ecology and evolution. In ecology and evolution, meta-analyses comparing two groups (usually experimental and control groups) have almost exclusively focused on comparing the means, using standardized metrics such as Cohen's / Hedges' d or the response ratio.2. However, an experimental treatment may not only affect the mean but also the variance. Investigating differences in the variance between two groups may be informative, especially when a treatment influences the variance in addition to or instead of the mean.3. In this paper, we propose the effect size statistic lnCVR (the natural logarithm of the ratio between the coefficients of variation, CV, from two groups), which enables us to meta-analytically compare differences between the variability of two groups. We illustrate the use of lnCVR with examples from ecology and evolution.4. Further, as an alternative approach to the use of lnCVR, we propose the combined use of ln s (the log standard deviation) and ln x (the log mean) in a hierarchical (linear mixed) model. The use of ln s with ln x ="false" overcomes potential limitations of lnCVR and it provides a more flexible, albeit more complex, way to examine variation beyond two-group comparisons. Relevantly, we also refer to the potential use of ln s and lnCV (the log CV) in the context of comparative analysis.5. Our approaches to compare variability could be applied to already published meta-analytic data sets that compare two-group means to uncover potentially overlooked effects on the variance. Additionally, our approaches should be applied to future meta-analyses, especially when one suspects a treatment has an effect not only on the mean, but also on the variance. Notably, the application of the proposed methods extends beyond the fields of ecology and evolution.