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How much does the typical ecological meta-analysis overestimate the true mean effect size?

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  • 1Department of Biological Sciences University of Calgary Calgary Alberta Canada.

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|November 21, 2022
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Summary

Small ecological studies often yield imprecise results. A new meta-meta-analysis method corrects for overestimations in ecological meta-analyses, improving effect size accuracy, especially for smaller studies.

Keywords:
best linear unbiased predictionseffect sizehierarchical modelmeta‐analysismeta‐meta‐analysisrandom effectsshrinkage

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Area of Science:

  • Ecology
  • Statistical Methods

Background:

  • Primary ecological studies frequently lack statistical power, leading to imprecise effect size estimates.
  • Meta-analyses combine studies but can still produce imprecise mean effect sizes, particularly with few contributing studies.

Purpose of the Study:

  • To propose and evaluate a method for estimating and correcting regression to the mean in ecological meta-analyses.
  • To improve the accuracy of mean effect size estimates in ecological research.

Main Methods:

  • Utilized meta-meta-analysis (a meta-analysis of meta-analyses) with a hierarchical random effects model.
  • Applied the method to a compilation of hundreds of ecological meta-analyses.

Main Results:

  • The typical ecological meta-analysis overestimates the true mean effect size magnitude by approximately 10%.
  • Small meta-analyses can overestimate true effect size magnitude by over 50% due to regression to the mean.

Conclusions:

  • Meta-meta-analysis effectively shrinks estimated mean effect sizes towards a grand mean, enhancing accuracy.
  • This approach is particularly valuable for refining estimates from meta-analyses with a limited number of studies.