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Asymptotic approximations for the radial plot in meta analysis, and a bias correction to the Egger test

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Copas, John B. and Lozada-Can, Claudia (2007) Asymptotic approximations for the radial plot in meta analysis, and a bias correction to the Egger test. Working Paper. Coventry: University of Warwick. Centre for Research in Statistical Methodology. Working papers, Vol.2007 (No.1).

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Official URL: http://www2.warwick.ac.uk/fac/sci/statistics/crism...

Abstract

Fixed effects meta analysis can be thought of as least squares analysis of the radial
plot, the plot of standardized treatment effect against precision (reciprocal of the standard
deviation) for the studies in a systematic review. For example, the Egger test for publication
bias is equivalent to testing the significance of the intercept in linear regression. In practice,
both x- and y-coordinates of the points in a radial plot are subject to sampling error, which
may be correlated, and so the standard theory of least squares does not apply. For the
Egger test, the actual significance levels are inflated, sometimes substantially so. We derive
approximations to the sampling properties of the radial plot, assuming that the within-
study sample sizes are large. This leads to an asymptotic bias correction for the Egger test.
A simulation study suggests that the bias correction controls the significance level of the
Egger test without any appreciable loss of power in detecting non-random study selection.
A clinical trials example is used as an illustration.

Item Type:

Working or Discussion Paper (Working Paper)

Subjects:

Q Science > QA Mathematics

Divisions:

Faculty of Science > Statistics

Library of Congress Subject Headings (LCSH):

Meta-analysis, Least squares, Clinical trials -- Mathematical models

Series Name:

Working papers

Publisher:

University of Warwick. Centre for Research in Statistical Methodology

Place of Publication:

Coventry

Official Date:

2007

Dates:

Date	Event
2007	Published

Volume:

Vol.2007

Number:

No.1

Number of Pages:

Status:

Not Peer Reviewed

Access rights to Published version:

Open Access

References:

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