[R-meta] Meta-analysis Hedges g - comparisons with same placebo

[P. Roberto Bakker]

It is a nice code. Thank you.

Some questons:
1. N1 is not always n1i+n2i - how can I interpret this?

2. I am analysing standardized mean deference *change* - I suppose I can
use the syntax also, correct?

Cheers, Roberto

2017-10-19 10:26 GMT+02:00 Viechtbauer Wolfgang (SP) <
wolfgang.viechtbauer at maastrichtuniversity.nl>:

> There is also code for computing the covariance among the standardized
> mean differences in such 'multitreatment' studies here:
>
> http://www.metafor-project.org/doku.php/analyses:gleser2009
>
> Best,
> Wolfgang
>
> -----Original Message-----
> From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-
> bounces at r-project.org] On Behalf Of Gerta Ruecker
> Sent: Wednesday, 18 October, 2017 13:28
> To: P. Roberto Bakker
> Cc: r-sig-meta-analysis at r-project.org
> Subject: Re: [R-meta] Meta-analysis Hedges g - comparisons with same
> placebo
>
> As I wrote in my response, see our paper
> http://onlinelibrary.wiley.com/doi/10.1002/jrsm.1259/full
> <http://onlinelibrary.wiley.com/doi/10.1002/jrsm.1259/full> .
>
> Best,
>
> Gerta
>
> Am 18.10.2017 um 13:10 schrieb P. Roberto Bakker:
> > Hi Gerta,
> >
> > Thank you for your reply and suggestions.
> > Our meta-analysis is not a network meta-analysis but a 'regular', i.e.
> > pairwise. Do you have suggestion how to adjust for this?
> > Bw,
> > Roberto
> >
> > Op 18 okt. 2017 10:41 a.m. schreef "Gerta Ruecker"
> > <ruecker at imbi.uni-freiburg.de <mailto:ruecker at imbi.uni-freiburg.de>>:
> >
> >     Dear Roberto,
> >
> >     it is a network meta-analysis what you are planning? Do you think of
> >     multi-arm studies including a placebo group? If so, and if it is the
> >     same placebo that is compared to several antidepressants, then I
> think
> >     there is no problem. The different placebo groups in different
> studies
> >     provide independent information and network meta-analysis may in fact
> >     increase precision (provided you have loops in your network), but
> this
> >     is exactly what network meta-analysis is intended to do.
> >
> >     To avoid misunderstandings: What you should not do is to use a
> placebo
> >     group in a multi-arm study twice in a pairwise meta-analysis without
> >     adjustment.
> >
> >     For an introduction, see
> >     http://onlinelibrary.wiley.com/doi/10.1002/jrsm.1259/full
> >     <http://onlinelibrary.wiley.com/doi/10.1002/jrsm.1259/full> .
> >
> >     Best,
> >
> >     Gerta
> >
> >
> >     --
> >
> >     Dr. rer. nat. Gerta Rücker, Dipl.-Math.
> >
> >     Medical Faculty and Medical Center - University of Freiburg
> >     Institute for Medical Biometry and Statistics
> >
> >     Stefan-Meier-Strasse 26, D-79104 Freiburg, Germany
> >
> >     Phone +49 (0)761 2036673 <tel:%2B49%20%280%29761%202036673>
> >     Fax +49 (0)761 2036680 <tel:%2B49%20%280%29761%202036680>
> >
> >     Mailruecker at imbi.uni-freiburg.de
> >     <mailto:Mailruecker at imbi.uni-freiburg.de>
> >     Webwww.imbi.uni-freiburg.de/biom/
> >     <http://Webwww.imbi.uni-freiburg.de/biom/>
> >
> >
> >     Am 18.10.2017 um 08:12 schrieb P. Roberto Bakker:
> >     > Hi,
> >     >
> >     > We are conducting a meta-analysis of RCTs between
> >     antidepressants and placebo and calculate Hedges g.
> >     > Question:
> >     > How can we deal with studies which compare different
> >     antidepressants with the same placebo? Our concern is when we
> >     include the different antidepressant comparisons with the same
> >     placebo in the meta-analysis the placebo size will increase
> >     artificially which will lead to more precise spurious results. If
> >     our reasoning is correct, how can we deal this?
> >     >
> >     > Thank you in advance,
> >     >
> >     > Roberto
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