If you are considering doing a systematic review or meta-analysis, this step-by-step guide aims to support you along the way.
The fixed effect model provides a weighted average of a series of study estimates.
The inverse of the estimates' variance is commonly used as study weight, so that larger studies tend to contribute more than smaller studies to the weighted average.
Consequently, when studies within a meta-analysis are dominated by a very large study, the findings from smaller studies are practically ignored.
Most importantly, the fixed effects model assumes that all included studies investigate the same population, use the same variable and outcome definitions, etc.
PRISMA provides guidance on what you should include when reporting a systematic review. Acknowledgements and References Much of this advice is based on the excellent (and extensive) guidance from the Cochrane Collaboration ( ) and the Centre for Reviews and Dissemination at York ( Rev/!
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Graphical summary of a meta analysis of over 1,000 cases of diffuse intrinsic pontine glioma and other pediatric gliomas, in which information about the mutations involved as well as generic outcomes were distilled from the underlying primary literature.On the other hand, indirect aggregate data measures the effect of two treatments that were each compared against a similar control group in a meta-analysis.For example, if treatment A and treatment B were directly compared vs placebo in separate meta-analyses, we can use these two pooled results to get an estimate of the effects of A vs B in an indirect comparison as effect A vs Placebo minus effect B vs Placebo.By reducing IPD to AD, two-stage methods can also be applied when IPD is available; this makes them an appealing choice when performing a meta-analysis.Although it is conventionally believed that one-stage and two-stage methods yield similar results, recent studies have shown that they may occasionally lead to different conclusions.However, in performing a meta-analysis, an investigator must make choices which can affect the results, including deciding how to search for studies, selecting studies based on a set of objective criteria, dealing with incomplete data, analyzing the data, and accounting for or choosing not to account for publication bias. Conceptually, a meta-analysis uses a statistical approach to combine the results from multiple studies in an effort to increase power (over individual studies), improve estimates of the size of the effect and/or to resolve uncertainty when reports disagree.Judgment calls made in completing a meta-analysis may affect the results. A meta-analysis is a statistical overview of the results from one or more systematic reviews.In addition to providing an estimate of the unknown common truth, meta-analysis has the capacity to contrast results from different studies and identify patterns among study results, sources of disagreement among those results, or other interesting relationships that may come to light in the context of multiple studies.A key benefit of this approach is the aggregation of information leading to a higher statistical power and more robust point estimate than is possible from the measure derived from any individual study.IPD evidence represents raw data as collected by the study centers.This distinction has raised the need for different meta-analytic methods when evidence synthesis is desired, and has led to the development of one-stage and two-stage methods.