# Doing Meta-Analysis in R

*A Hands-on Guide*

*¹Friedrich-Alexander-University Erlangen-Nuremberg, ²Vrije Universiteit Amsterdam, ³Kyoto University*

# Chapter 1 About this Guide

This guide shows you how to conduct meta-analyses in *R* from scratch. The focus of this guide is primarily on clinical outcome research in psychology. It was designed for staff and collaborators of the **Protect Lab**, which is headed by **Prof. Dr. David D. Ebert**.

#### The guide will show you how to:

- Get
*R*and**RStudio**set for your Meta-Analysis. - Get your data into
*R*. **Prepare your data**for the meta-analysis.- Install and use the
`dmetar`

*R*package we built specifically for this guide. - Perform
**fixed-effect**and**random-effects**meta-analysis using the`meta`

and`metafor`

packages. - Analyse the
**heterogeneity**of your results. - Tackle heterogeneity using
**subgroup analyses**and**meta-regression**. - Check if
**selective outcome reporting (publication bias)**or \(p\)**-hacking**is present in your data. - Summarize the
**risk of bias**of your study material. - Calculate the
**power**of a meta-analysis. **Convert effect sizes**reported in original studies to the ones you need for your meta-analysis.- Do advanced types of meta-analyses, such as
**multilevel meta-analyses****multivariate meta-analyses****meta-analytic structural equation modeling**or**network meta-analyses**.

#### What this guide will not cover

Although this guide will provide some information on the statistics behind meta-analysis, it will not give you an **in-depth introduction** into how meta-analyses are calculated statistically.

It is also beyond the scope of this guide to advise in detail which meta-analytical strategy is suited best in which contexts, and on how the search, study inclusion and reporting of meta-analyses should be conducted. The *Cochrane Handbook for Systematic Reviews of Interventions*, however, should be a great source to find more information on these topics.

#### Other sources to recommend when conducting Meta-Analyses

- If you are looking for an easily digestable, hands-on introduction on how Meta-Analyses are conducted, we can recommend
**Pim Cuijpers’ online courses on meta-analysis**. The courses are freely available on YouTube. To have a look, click here. The course is based on a**book**(Cuijpers 2016), which you can download for free here. - If you are interested in more details on how to conduct meta-analyses in
*R*, you can either have a look at Wolfgang Viechtbauer’s webpage for the`metafor`

package (Link). Or you can consult a book written by Schwarzer and colleagues on the`meta`

package (Schwarzer, Carpenter, and Rücker 2015). We can also recommend a book written by**Terri Pigott**, which focuses more on the theoretical background of and advances in meta-analytic techniques (Pigott 2012).

**How to get the R code for this guide**

All code behind this book is available online on **GitHub**. We have created a website containing a **download link** for all material, and a **quick guide** on how to get the *R* code presented in this book running on your computer. The site can be found here.

#### How to cite this guide

Harrer, M., Cuijpers, P., Furukawa, T.A, & Ebert, D. D. (2019). Doing Meta-Analysis in R: A Hands-on Guide. https://bookdown.org/MathiasHarrer/Doing_Meta_Analysis_in_R/. . Citation Download

**To get started, proceed to the next chapter!**

### License

Doing Meta-Analysis in R: A Hands-On Guide by Mathias Harrer, Pim Cuijpers, Toshi Furukawa and David Ebert is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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### Contributors

This guide is an open project, and we owe special thanks to our expert contributors who provided additional content in some of the sections of this guide.

**Luke A. McGuinness, M.Sc.**, University of Bristol: Chapter 10, Risk of Bias Plots.

Want to contribute to this guide yourself? Feel free to send **Mathias** (mathias.harrer@fau.de) an E-mail and tell us about your proposed additions.

### References

Cuijpers, Pim. 2016. “Meta-Analyses in Mental Health Research. A Practical Guide.” *Amsterdam, the Netherlands: Pim Cuijpers Uitgeverij*.

Schwarzer, Guido, James R Carpenter, and Gerta Rücker. 2015. *Meta-Analysis with R*. Springer.

Pigott, Terri. 2012. *Advances in Meta-Analysis*. Springer.