Re: [R] Help conduction Egger's test

[Michael Dewey]

At 19:02 12/05/2014, Sultan Malik wrote:

Hi,

I am currently conducting a meta analyses and wish to carry out 
Egger's test. I was just wondering, does the weighted linear 
regression model proposed by Egger et al correspond to the weighted 
regression with multiplicative dispersion option in Metafor?


Dear Sultan

One thing I would suggest is to also use the ranktest function. In my 
experience they can give different results. You also need to look at 
the funnel plot of course and bear in mind that none of these methods 
is very satisfactory unless you have quite a number of fairly 
homogenous studies to synthesise.



Many thanks

Sultan


Michael Dewey
i...@aghmed.fsnet.co.uk
http://www.aghmed.fsnet.co.uk/home.html

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[R] Help conduction Egger's test

[Sultan Malik]

Hi, 

I am currently conducting a meta analyses and wish to carry out Egger’s test. I 
was just wondering, does the weighted linear regression model proposed by Egger 
et al correspond to the weighted regression with multiplicative dispersion” 
option in Metafor?

Many thanks

Sultan
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R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Re: [R] Help conduction Egger's test

[Viechtbauer Wolfgang (STAT)]

Yes, the 'traditional' Egger test is a weighted regression of the effect size 
estimates against their standard errors with weights s2/vi, where s2 is a 
multiplicative dispersion parameter. This is what you will get with:

regtest(x, model=lm, predictor=sei)

where 'x' is an object returned by the rma() function from a 
fixed/random-effects model.

An example:

### load BCG vaccine data
data(dat.bcg)

### calculate log relative risks and corresponding sampling variances
dat - escalc(measure=RR, ai=tpos, bi=tneg, ci=cpos, di=cneg, data=dat.bcg)

### random-effects model
res - rma(yi, vi, data=dat)

### classical Egger test
regtest(res, model=lm, predictor=sei)

Best,
Wolfgang

--   
Wolfgang Viechtbauer, Ph.D., Statistician   
Department of Psychiatry and Psychology   
School for Mental Health and Neuroscience   
Faculty of Health, Medicine, and Life Sciences   
Maastricht University, P.O. Box 616 (VIJV1)   
6200 MD Maastricht, The Netherlands   
+31 (43) 388-4170 | http://www.wvbauer.com   


 -Original Message-
 From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org]
 On Behalf Of Sultan Malik
 Sent: Monday, May 12, 2014 20:03
 To: r-help@r-project.org
 Subject: [R] Help conduction Egger's test
 
 Hi,
 
 I am currently conducting a meta analyses and wish to carry out Egger's
 test. I was just wondering, does the weighted linear regression model
 proposed by Egger et al correspond to the weighted regression with
 multiplicative dispersion option in Metafor?
 
 Many thanks
 
 Sultan
 __
 R-help@r-project.org mailing list
 https://stat.ethz.ch/mailman/listinfo/r-help
 PLEASE do read the posting guide http://www.R-project.org/posting-
 guide.html
 and provide commented, minimal, self-contained, reproducible code.

__
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.