[R-meta] Mean and SD or unstandardized regression coefficients?

[Stefanou Revesz]

Many thanks for the valuable insights.

Stefanou

On Tue, Nov 23, 2021 at 3:42 PM Lukasz Stasielowicz
<lukasz.stasielowicz using uni-osnabrueck.de> wrote:
>
> Dear Stefanou,
>
> as Michael Dewey has pointed out, comparing regression coefficients
> based on models with different sets of variables can be difficult as the
> meaning of the coefficients changes. Furthermore, adding certain
> variables can introduce suppression effects, which can sometimes change
> the sign of the regression coefficient. In the meta-analytic context it
> could introduce spurious heterogeneity (e.g., negative and positive
> regression coefficients).
>
> In addition, when one really wants to synthesize unstandarized
> regression coefficients then one has to ensure that the same instruments
> were used across studies or that the coding of the variables is
> consistent across studies, e.g. group is always coded as 0 = Control
> group and 1 = Intervention group, time scale is always the same (e.g.
> Study 1 - days, Study 2 - days vs. Study 1 - days, Study 2 - weeks) etc.
>
>
> See also:
> Becker, B. J., & Wu, M.-J. (2007). The synthesis of regression slopes in
> meta-analysis. Statistical Science, 22(3), 414–429.
> https://doi.org/10.1214/07-STS243
>
>
> Thus, synthesizing means or mean differences seems to be preferable. If
> there are enough studies then one could conduct additional analyses,
> e.g. synthesizing regression coefficients based on regression models
> with the same set of variables.
>
>
> Best wishes,
> Lukasz
> --
> Lukasz Stasielowicz
> Osnabrück University
> Institute for Psychology
> Research methods, psychological assessment, and evaluation
> Seminarstraße 20
> 49074 Osnabrück (Germany)
>
> Am 23.11.2021 um 12:18 schrieb r-sig-meta-analysis-request using r-project.org:
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> > Today's Topics:
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> >     1. Re: Mean and SD or unstandardized regression coefficients?
> >        (Michael Dewey)
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Mon, 22 Nov 2021 11:07:09 +0000
> > From: Michael Dewey <lists using dewey.myzen.co.uk>
> > To: Stefanou Revesz <stefanourevesz using gmail.com>, R meta
> >       <r-sig-meta-analysis using r-project.org>
> > Subject: Re: [R-meta] Mean and SD or unstandardized regression
> >       coefficients?
> > Message-ID: <45c857de-e284-0624-afb7-fe077fa5428c using dewey.myzen.co.uk>
> > Content-Type: text/plain; charset="utf-8"; Format="flowed"
> >
> > Dear Stefanou
> >
> > I suspect there may be different opinions here but it seems to me that
> > the advantage of the regression coefficients is that they provide a
> > better estimate of the effect but their disadvantage is that if primary
> > studies adjusted for different variables they are not estimating the
> > same thing. So depending on what they adjusted for I might choose either
> > of them under different circumstances.
> >
> > Michael
> >
> > On 21/11/2021 16:21, Stefanou Revesz wrote:
> >> Dear Meta-Analysis Experts,
> >>
> >> My sample of longitudinal studies both provide the raw descriptive
> >> statistics (mean, sd) for groups at different time points as well as
> >> the unstandardized regression coefficients for group*time interactions
> >> often adjusted for various confounding variables which may not be the
> >> same across the studies.
> >>
> >> To meta-analyze these studies, is it better to meta-analyze the
> >> adjusted unstandardized regression coefficients for group*time
> >> interactions or the raw (i.e., unadjusted) descriptive statistics
> >> (mean, sd) for groups at different time points?
> >>
> >> Thanks,
> >> Stefanou
> >>
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> >
>
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