[R-meta] Question on funnel plot interpretation

[Yefeng Yang]

Dear Gabriel

Apart from Michael observation on data checking before analyses (which is always a good practice), I add one.
The funnel plot is just a visual check of publication bias. So the observations based on the funnel plots are inevitably subjective - I mean you think that is "randomly scattering", while others might think not. In contrast, Egger's test is a more objective way to test the asymmetry of a funnel plot. Regarding how to do it, you can try to find them in the archives associated with this mailing list.

Please be noted that whether none funnel plot and Egger's test can indicate publication bias directly. But it is common to assume the asymmetry of a funnel plot is caused by publication bias (or more precisely. small study effects), after accounting for heterogeneity.

Best,
Yefeng
________________________________
From: R-sig-meta-analysis <r-sig-meta-analysis-bounces using r-project.org> on behalf of Michael Dewey via R-sig-meta-analysis <r-sig-meta-analysis using r-project.org>
Sent: Wednesday, 5 July 2023 19:31
To: R Special Interest Group for Meta-Analysis <r-sig-meta-analysis using r-project.org>
Cc: Michael Dewey <lists using dewey.myzen.co.uk>; Gabriel Cotlier <gabiklm01 using gmail.com>
Subject: Re: [R-meta] Question on funnel plot interpretation

Dear Gabriel

My interpretation looking at your plots is that you have a very strange
set of primary studies. If the x-axis is really the z transformation of
r then some of  the r are .999 and some 0.001 which seems worthy of
investigation before looking further.

Michael

On 05/07/2023 09:14, Gabriel Cotlier via R-sig-meta-analysis wrote:
> Hello all,
>
> I have produced a funnel plot on the basis of an rma.mv
> <http://rma.mv>() objectapplied to all the data set together ( not
> subsetting  using moderators ) as follows:
>
> image.png
>
>
> When looking at the figure I tried to think that maybe one of the
> following two interpretations could be the correct one:
>
> a.  There is a kind of random scattering of the effect sizes, therefore
> no symmetry is found and thus publication bised is observed.
> b.  Given the randomness of the effect sizes distribution covering the
> plot's space unevenly there is not a clear pattern that can indicate
> publication bias is observed.
>
> Is any of this interpretation the correct one?
>
> Thanks a lot.
> Kind regards,
> Gabriel
>
>
> #### CODE. ######
> funnel_all <- rma.mv <http://rma.mv>(yi,
>                       vi,
>                       random = ~ 1 | Article / Sample_ID,
>                       data=dat)
> png(file = "funnel.png",
>      width = 250,
>      height = 200,
>      res = 600,
>      units = "mm")
> # par(mfrow = c(2, 1))
>
> # full data
> f1 <- funnel(funnel_all,
>               yaxis = "seinv",
>               level = c(90, 95, 99),
>               ylim = c(1, 20),
>               shade = c("white", "gray55", "gray75"),
>               refline = 0,
>               legend = TRUE)
> mtext("A", side = 3, line = 0, adj = -0.13, cex = 2)
>
> dev.off()
>
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>  Virus-free.www.avg.com <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
>
> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>
> _______________________________________________
> R-sig-meta-analysis mailing list @ R-sig-meta-analysis using r-project.org
> To manage your subscription to this mailing list, go to:
> https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis

--
Michael
http://www.dewey.myzen.co.uk/home.html

_______________________________________________
R-sig-meta-analysis mailing list @ R-sig-meta-analysis using r-project.org
To manage your subscription to this mailing list, go to:
https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis

	[[alternative HTML version deleted]]