how to do a meta analysis
A meta-analysis is the use of statistical methods to summarise the results of these studies.
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Correspondence should be addressed to Professor Andy P. Field, School of Psychology, University of Sussex, Falmer, Brighton BN1 9QH, UK (e‐mail: [email protected]); or Raphael Gillett, School of Psychology, Henry Wellcome Building, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK (e‐mail: [email protected]).Search for more papers by this author
Considering that a systematic review  is fundamental for a meta-analysis, you can use the Population, Intervention, Comparison, Outcome (PICO) model to formulate the research question. It is important to verify that there are no published meta-analyses on the specific topic in order to avoid duplication of efforts . In some cases, an updated meta-analysis in a topic is needed if additional data become available. It is possible to carry out meta-analyses for multiple types of studies, such as epidemiological variables for case-control, cohort, and randomized clinical trials. As observational studies have a larger possibility of having several biases, meta-analyses of these types of designs should take that into account. In addition, there is the possibility to carry out meta-analyses for genetic association studies, gene expression studies, genome-wide association studies (GWASs), or data from animal experiments. It is advisable to preregister the systematic review protocols at the International Prospective Register of Systematic Reviews (PROSPERO; https://www.crd.york.ac.uk/Prospero) database . Keep in mind that an increasing number of journals require registration prior to publication.
Copyright: © 2019 Forero et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Meta-analysis is widely accepted as the preferred method to synthesize research findings in various disciplines. This paper provides an introduction to when and how to conduct a meta-analysis. Several practical questions, such as advantages of meta-analysis over conventional narrative review and the number of studies required for a meta-analysis, are addressed. Common meta-analytic models are then introduced. An artificial dataset is used to illustrate how a meta-analysis is conducted in several software packages. The paper concludes with some common pitfalls of meta-analysis and their solutions. The primary goal of this paper is to provide a summary background to readers who would like to conduct their first meta-analytic study.
Keywords: Literature review; Meta-analysis; Moderator analysis; Systematic review.
Meta-analyses began to appear as a leading part of research in the late 70s. Since then, they have become a common way for synthesizing evidence and summarizing the results of individual studies (2).
By combining individual studies, and thus using more data, the precision and accuracy of the estimates in the individual studies can be improved upon. Additionally, if the individual studies were underpowered, combining them in a meta-analysis can increase the overall statistical power to detect an effect.