Funnel plot
A funnel plot is a graph designed to check for the existence of publication bias; funnel plots are commonly used in systematic reviews and 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.
Quotation
Funnel plots, introduced by Light and Pillemer in 1984[1] and discussed in detail by Matthias Egger and colleagues,[2][3] are useful adjuncts to meta-analyses. A funnel plot is a
A variety of choices of measures of ‘study precision’ is available, including total sample size,
In common with confidence interval plots, funnel plots are conventionally drawn with the treatment effect measure on the horizontal axis, so that study precision appears on the vertical axis, breaking with the general rule. Since funnel plots are principally visual aids for detecting asymmetry along the treatment effect axis, this makes them considerably easier to interpret.
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.[4] The appearance of the funnel plot can change quite dramatically depending on the scale on the y-axis — whether it is the inverse square error or the trial size.[5] Researchers have a poor ability to visually discern publication bias from funnel plots.[6]
See also
References
- ISBN 978-0-674-85431-4.
- PMID 9310563.)
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- PMID 16974018.)
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: CS1 maint: multiple names: authors list (link - PMID 10812319.
- PMID 16085192.
Further reading
- Sterne, J. A. C.; Sutton, A. J.; Ioannidis, J. P. A.; et al. (2011), "Recommendations for examining and interpreting funnel plot asymmetry in meta-analyses of randomised controlled trials", BMJ, 343: d4002, PMID 21784880
- Higgins, J.P.T.; Thomas, J.; Chandler, J.; Cumpston, M.; Li, T.; Page, M.J.; Welch, V.A. (2019), Cochrane handbook for systematic reviews of interventions (2nd ed.), Wiley Blackwell, ISBN 9781119536611