Help conduction Egger's test

classic Classic list List threaded Threaded
3 messages Options
Reply | Threaded
Open this post in threaded view
|

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
______________________________________________
[hidden email] 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.
Reply | Threaded
Open this post in threaded view
|

Re: Help conduction Egger's test

Wolfgang Viechtbauer-2
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: [hidden email] [mailto:[hidden email]]
> On Behalf Of Sultan Malik
> Sent: Monday, May 12, 2014 20:03
> To: [hidden email]
> 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
> ______________________________________________
> [hidden email] 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.

______________________________________________
[hidden email] 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.
Reply | Threaded
Open this post in threaded view
|

Re: Help conduction Egger's test

Michael Dewey
In reply to this post by Sultan Malik
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
[hidden email]
http://www.aghmed.fsnet.co.uk/home.html

______________________________________________
[hidden email] 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.