Funnel plot: Difference between revisions

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{{Short description|Type of graph used in research}}

[[File:Funnelplot.png|thumb|right|An example funnel plot showing no publication bias. Each dot represents a study (e.g. measuring the effect of a certain drug); the ''y''-axis represents study precision (e.g. the [[Precision (statistics)|precision]] (e.g. the inverse standard error) or number of experimental subjects) and the ''x''-axis shows the study's result (e.g. the drug's measured average effect).]]

A '''funnel plot''' is a graph designed to check for the existence of [[publication bias]]; funnel plots are commonly used in [[systematic review]]s and [[meta-analysis|meta-analyses]]. In the absence of publication bias, it assumes that studies with high precision will be plotted near the average, and studies with low precision will be spread evenly on both sides of the average, creating a roughly [[funnel]]-shaped distribution. Deviation from this shape can indicate publication bias.

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== Criticism ==

The funnel plot is not without problems.

If high -precision studies are different from low -precision studies with respect to [[effect size]] (e.g., due to different populations examined) a funnel plot may give a wrong impression of publication bias.<ref>{{Cite journal

| author = Joseph Lau, [[John P. A. Ioannidis]], Norma Terrin, Christopher H. Schmid & [[Ingram Olkin]]

| title = The case of the misleading funnel plot

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| doi = 10.1016/S0895-4356(99)00204-8

| pmid=10812319

}}</ref> Researchers have a poor ability to visually discern publication bias from funnel plots.<ref>{{Cite journal|last1=Terrin|first1=N.|last2=Schmid|first2=C. H.|last3=Lau|first3=J.|year=2005|title=In an empirical evaluation of the funnel plot, researchers could not visually identify publication bias|url=https://www.jclinepi.com/article/S0895-4356(05)00082-X/abstract|journal=Journal of Clinical Epidemiology|language=English|volume=58|issue=9|pages=894–901|doi=10.1016/j.jclinepi.2005.01.006|issn=0895-4356|pmid=16085192|url-access=subscription}}</ref>

== See also ==