META-ANALYSIS IN R

July 8, 2024

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This webpage is a collection of resources (links, slides, data, and R code) for the one-day seminar on ‘Meta-analysis in R’ conducted by Enrico Toffalini on July 8, 2024, for PhD students in Social Sciences at the University of Genova.

Questions that will be addressed:

• What is a “meta-analysis”?

• What is the difference between a meta-analysis and a systematic review? (and what “standard” do you have to follow when doing a “systematic review with meta-analysis”?)

• What are effect sizes and how do you interpret them? (real-life examples of standardized vs unstandardized effect sizes?)

• What is “heterogeneity” of effect sizes in a meta-analysis?

• Why might a meta-analysis present a “multilevel” structure?

• What is a “moderator” in a meta-analysis? (examples? when are moderators important and how do you assess them?)

• What is a “publication bias” and why is it an issue in meta-analysis?

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Slides

• Understanding effect sizes: from simple (correlations, cohen’s d) to complex (mixed models, glm/glmer)

• Understanding the variance of effect sizes

• General introduction to meta-analysis (by Gambarota & Altoè)

• Understanding heterogeneity in meta-analysis with examples

• Meta-analyzing Correlations: From structuring the dataset to (not actually so) basic analyses

• Meta-analyzing SMD / Cohen’s d: From structuring the dataset to (not actually so) basic analyses

• Multilevel models in meta-analysis (by Harrer)

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Exercises

• Exercise 1: Simulated dataset

• Exercise 2: Simulated dataset, more complex, with MLMA and moderators

• Exercise 2: (real shared dataset) Anxiety and Math performance open and publicly shared dataset for the article by Caviola et al. (2022)

• Exercise 3: (real shared dataset) Dyslexia treatment efficacy open and publicly shared dataset for the article by Toffalini et al. (2021)

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Resources

Books

• Borenstein, M., Hedges, L. V., Higgins, J. P. T., & Rothstein, H. R. (2009). Introduction to Meta-Analysis. https://doi.org/10.1002/9780470743386

Websites

• metasimulation: Great series of slides and other resources on meta-analyses and related topics by Filippo Gambarota and Gianmarco Altoè (University of Padova).

• Mathias Harrer: Doing Meta-Analysis in R a fabulous website covering virtually all relevant meta-analysis-related topics in the form of a hands-on guide.

• metafor: website of reference for the famous metafor package, with lots of examples, pages, and code.

• Viechtbauer: personal website of Wolfgang Viechtbauer (i.e., the mythological creator of the “metafor” package)

Github repositories

• metasimulation github: all materials for the above “metasimulation” website (by Gambarota & Altoè)

• metafor github: the whole legendary “metafor” package on github, with lots of code and documentation

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