Making Meta-Analyses “Open”: A How-To

[Excerpts taken from the article “Conducting a Meta-Analysis in the Age of Open Science: Tools, Tips, and Practical Recommendations” by David Moreau and Beau Gamble, posted at PsyArXiv Preprints]
“In this tutorial, we describe why open science is important in the context of meta-analysis in psychology, and suggest how to adopt the three main components of open science: preregistration, open materials, and open data.”
“We first describe how to make the preregistration as thorough as possible—and how to handle deviations from the plan.”
“We then focus on creating easy-to-read materials (e.g., search syntax, R scripts) to facilitate reproducibility and bolster the impact of a meta-analysis.”
“Finally, we suggest how to organize data (e.g., literature search results, data extracted from studies) that are easy to share, interpret, and update as new studies emerge. “
“For each component, we provide templates that can help standardization while allowing the necessary flexibility to accommodate idiosyncrasies across meta-analyses (see Fig. 1 for an overview).”
“All templates—together with tips on how to best utilize them—are also illustrated with step-by-step video tutorials, in an effort to facilitate systematic implementation in psychology. For each step of the meta-analysis, we provide example templates, accompanied by brief video tutorials…”
Figure 1. Flow chart describing all the provided templates for creating a transparent meta-analysis.TRN(20200120)
“In the context of meta-analyses…preregistration might seem particularly challenging. How can one know what studies are relevant before running the search, for instance? Will five databases be comprehensive enough, or overkill? What moderator analyses will have enough statistical power? And what methods should be used to detect bias? To facilitate the process of preregistration, we provide a list of items to consider, together with a brief explanation for each, in Template 1…”
“The template is designed to enable flexible yet thorough preregistration, specifically in the context of meta-analyses in psychology. The items follow the PRISMA protocol, but also contain tips and examples specific to our field. We also provide a ready-to-populate flow diagram that adheres to the PRISMA protocol (Template 2).”
“The flow diagram is a visual depiction of the search process in a meta-analysis, from the initial query to the final selection of studies, and including all steps in between. This component is key for transparency, as it provides a quick overview of the data collection process, and serves as a reference document to navigate possible intricacies of the design.”
Open Materials
“A central component of open material relates to sharing scripts for data wrangling and analyses…we provide examples in R, given its appeal for reproducibility and its widespread use in psychology. We designed a generic script (Template 3) that requires minimal tailoring for each individual meta-analysis.”
“To promote reproducibility, it is also crucial to document the exact search syntax used for all databases. We provide a search syntax template that can accommodate different databases, and that has been prepopulated with an example from psychology (Template 4).”
“A thorough meta-analysis often includes articles or reports that were not directly available online…This is an important step, as it helps correct for some of the overall publication bias.”
“In the process of accessing all possible data, a researcher often has to contact authors directly…To facilitate these requests, we provide two email templates that have been worded carefully to ensure the rationale of the request is clear and that authors understand what the project will entail.”
“These templates include an open call for data, to email authors in the field during the initial stage of the search (Template 5), and a specific data request, to email authors of studies that appear to be relevant, but lack information or require clarification (Template 6).”
Open Data
Template 7 has been designed to allow sharing all content relevant to the search results, thus increasing transparency and facilitating reproducibility. Information such as decisions to include or exclude a study, ambiguities, and the overall breakdown of articles across databases can be documented in this file.”
“In addition, we provide a template to store all data extracted from the search, after it has been curated (Template 8). The template includes metadata about each reference, descriptive statistics, as well as notes and additional information for each study.”
“Finally, regardless of how thoroughly planned a meta-analysis is, researchers will almost inevitably deviate from the original plan.”
“Keeping a record of all deviations from the original protocol is key to facilitate assessment by editors, reviewers, and readers. This record should include the specifics of what has been changed, and the extent of the change.”
“For example, if one changes a preregistered criterion on outlier detection, perhaps because it appears too stringent, it is important to state the difference between the two criteria, as well as the extent to which this impacts the results and the interpretation of the findings.”
“Deviations also need to be justified, that is, a rationale as to why the change was necessary or desired should be provided…Template 9 allows documenting and justifying deviations from planned protocols, and shows some fictional examples from psychology.”
“In this tutorial, we presented a rationale for open science practices in the context of meta-analysis, specifically focused on preregistration, open materials and open data. In an effort to facilitate broad impact and readability, we provided nine standardized templates with tips and recommendations.”
To read the article and access the templates, click here.

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