[R-meta] Compiling different design in the same met-analysis

Mon, May 3, 2021 11:09 AM

Hi Gladys,

You may pool all effects in a meta-analysis, using "design" as a 
moderator. In meta-analysis, this is called a subgroup analysis (for 
example by Cochrane). You then get both within-subgroup effects and a 
pooled effect, and also a test of treatment--design interaction, that 
says whether the treatment effect is different between designs. Thus you 
have all what you are interested in. However, in your interpretation you 
have to account for the different character of the studies: In a 
two-group parallel design, if it is randomized (you did not mention 
whether it is), you can expect an unbiased estimate of the treatment 
effect. In a pre-post design, you must expect all kinds of biases (to 
mention only regression to the mean) and also, as Michael said, 
different variation. Therefore you have to interpret results with caution.

Best, Gerta

Am 03.05.2021 um 19:42 schrieb Gladys Barragan-Jason:

Hi Gerta and Michael,
I am not sure to understand. I am not saying the the effect size are 
different. They are comparable but of course differ in term of ci 
since the number of studies, participants are different. I would like 
to know whether we can make obtain an overall effect size while 
controlling for design. So maybe the answer is no.
Thanks
Gladys

Le lun. 3 mai 2021 ? 19:11, Dr. Gerta R?cker 
<ruecker at imbi.uni-freiburg.de <mailto:ruecker at imbi.uni-freiburg.de>> a 
?crit?:

    Technically, you may conduct a meta-analysis of these two effects and
    obtain something between. The question is how to interpret this.

    Best,

    Gerta

    Am 03.05.2021 um 19:06 schrieb Michael Dewey:

    > Yes, exactly. After all if you show two things are different you
    > cannot say they are the same.
    >
    > Michael
    >
    > On 03/05/2021 15:59, Gladys Barragan-Jason wrote:

    >> Okay, so you can't obtain an overall effect size while controlling
    >> for design?
    >>
    >> Le lun. 3 mai 2021 ? 14:36, Michael Dewey

    <lists at dewey.myzen.co.uk <mailto:lists at dewey.myzen.co.uk>

    >> <mailto:lists at dewey.myzen.co.uk

    <mailto:lists at dewey.myzen.co.uk>>> a ?crit?:

    >>
    >> ??? If you include a moderator you do not get an overall effect
    >> because by
    >> ??? including it you are effectively saying there is no single

    overall

    >> ??? effect.
    >>
    >> ??? On 03/05/2021 12:24, Gladys Barragan-Jason wrote:
    >> ???? > Hi Michael,
    >> ???? > Thanks a lot for your quick response. Here are answers

    and other

    >> ???? > questions below.
    >> ???? >
    >> ???? > Le?lun. 3 mai 2021 ??12:41, Michael Dewey
    >> ??? <lists at dewey.myzen.co.uk <mailto:lists at dewey.myzen.co.uk>

    <mailto:lists at dewey.myzen.co.uk <mailto:lists at dewey.myzen.co.uk>>

    >> ???? > <mailto:lists at dewey.myzen.co.uk

    <mailto:lists at dewey.myzen.co.uk>

    >> ??? <mailto:lists at dewey.myzen.co.uk

    <mailto:lists at dewey.myzen.co.uk>>>> a ?crit?:

    >> ???? >
    >> ???? >? ? ?Dear Gladys
    >> ???? >
    >> ???? >? ? ?Comments in-line
    >> ???? >
    >> ???? >? ? ?On 03/05/2021 08:13, Gladys Barragan-Jason wrote:
    >> ???? >? ? ? > Dear all,
    >> ???? >? ? ? >
    >> ???? >? ? ? > I am doing a meta-analysis on experimental data

    on the

    >> ??? impact on
    >> ???? >? ? ? > several?behavioral interventions including both

    *pre-post

    >> ??? studies*
    >> ???? >? ? ? > (measurement of a trait before and after the

    intervention)

    >> ??? *and
    >> ???? >? ? ?control
    >> ???? >? ? ? > vs. treatment studies *(measurement?after a control
    >> ??? intervention vs.
    >> ???? >? ? ? > measurement after the intervention).
    >> ???? >
    >> ???? >? ? ?So the first design just has one group which is measured
    >> ??? twice and the
    >> ???? >? ? ?second design has two parallel groups which are each

    measured

    >> ??? once?
    >> ???? >
    >> ???? >
    >> ???? > Exactly!
    >> ???? >
    >> ???? >
    >> ???? >? ? ? > I am interested in the effect size of each type of
    >> ??? intervention on a
    >> ???? >? ? ? > specific trait that is common to all studies.
    >> ???? >? ? ? >
    >> ???? >? ? ? > I would like to know whether?it is correct to

    compile all

    >> ??? studies
    >> ???? >? ? ?from
    >> ???? >? ? ? > one type of intervention (whatever?the type of
    >> comparisons:
    >> ???? >? ? ?pre-pot and
    >> ???? >? ? ? > control vs. treatment group together) with pre- and
    >> ??? control being as
    >> ???? >? ? ? > control and post and treatment being as treatment.
    >> ???? >? ? ? >
    >> ???? >
    >> ???? >? ? ?I do not think that is going to work well. Although

    the two

    >> ??? designs
    >> ???? >? ? ?could be considered as estimating the same effect their
    >> ??? variability
    >> ???? >? ? ?should be very different since in design 1 you have

    reduced

    >> ??? the effect
    >> ???? >? ? ?of individual variability. If you do include both

    designs

    >> in one
    >> ???? >? ? ?analysis I would have thought it mandatory to include a
    >> ??? moderator with
    >> ???? >? ? ?two levels for design.
    >> ???? >
    >> ???? > This makes sense. When I do this, I then obtain two

    effect sizes

    >> ??? (one
    >> ???? > for each design); (in having mods=~design-1). Do you

    know how I

    >> ??? can get
    >> ???? > the overall effect size?
    >> ???? >
    >> ???? >
    >> ???? >? ? ? > I have a second question about how to thank the
    >> ???? >? ? ? > r-sig-meta-analysis at r-project.org

    <mailto:r-sig-meta-analysis at r-project.org>

    >> ??? <mailto:r-sig-meta-analysis at r-project.org

    <mailto:r-sig-meta-analysis at r-project.org>>

    >> ???? >? ? ?<mailto:r-sig-meta-analysis at r-project.org

    <mailto:r-sig-meta-analysis at r-project.org>

    >> ??? <mailto:r-sig-meta-analysis at r-project.org

    <mailto:r-sig-meta-analysis at r-project.org>>>

    >> ???? >? ? ? > <mailto:r-sig-meta-analysis at r-project.org

    <mailto:r-sig-meta-analysis at r-project.org>

    >> ??? <mailto:r-sig-meta-analysis at r-project.org

    <mailto:r-sig-meta-analysis at r-project.org>>

    >> ???? >? ? ?<mailto:r-sig-meta-analysis at r-project.org

    <mailto:r-sig-meta-analysis at r-project.org>

    >> ??? <mailto:r-sig-meta-analysis at r-project.org

    <mailto:r-sig-meta-analysis at r-project.org>>>> list for all their help

    >> ???? >? ? ? > (acknowledgements?in a paper).
    >> ???? >
    >> ???? >? ? ?I would have thought the URL
    >> ???? > https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis//
    >> <https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis//>
    >> ???? >

    ?<https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis//

    >> <https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis//>>
    >> ???? >? ? ?was better. How to do this will also depend on

    custom and

    >> ??? practice in
    >> ???? >? ? ?your scientific discipline, some journals in mine

    require

    >> ??? people who
    >> ???? >? ? ?are
    >> ???? >? ? ?acknowledged to give their consent.
    >> ???? >
    >> ???? >
    >> ???? > Ok! Thanks a lot!
    >> ???? >
    >> ???? > Best,
    >> ???? > Gladys
    >> ???? >
    >> ???? >
    >> ???? >? ? ?Michael
    >> ???? >
    >> ???? >? ? ? >
    >> ???? >? ? ? > Thanks a lot for your help!
    >> ???? >? ? ? >
    >> ???? >? ? ? > Have a great day,
    >> ???? >? ? ? >
    >> ???? >? ? ? > Gladys
    >> ???? >? ? ? >
    >> ???? >? ? ? > --
    >> ???? >? ? ? >
    >> ???? >? ? ? > ------------------------------------------
    >> ???? >? ? ? >
    >> ???? >? ? ? > Gladys Barragan-Jason, PhD. ____?Website
    >> ???? >? ? ? >

    <https://sites.google.com/view/gladysbarraganjason/home

    >> <https://sites.google.com/view/gladysbarraganjason/home>
    >> ???? > ?<https://sites.google.com/view/gladysbarraganjason/home
    >> <https://sites.google.com/view/gladysbarraganjason/home>>>
    >> ???? >? ? ? >
    >> ???? >? ? ? > Station d'Ecologie Th?orique et Exp?rimentale

    (SETE)____

    >> ???? >? ? ? >
    >> ???? >? ? ? > CNRS de Moulis____
    >> ???? >? ? ? >
    >> ???? >? ? ? > image.pngimage.png____
    >> ???? >? ? ? >
    >> ???? >? ? ? >
    >> ???? >? ? ? >
    >> ???? >? ? ? >
    >> ???? >? ? ? >
    >> ???? >
    >>

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    >> ???? >
    >>

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    >>
    >> ???? >
    >> ???? >? ? ? >? ? ? ?Virus-free. www.avg.com

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    >>
    >> ???? >
    >> ???? >? ? ? >
    >> ???? >? ? ? >
    >> ???? >? ? ? > <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
    >> ???? >? ? ? >
    >> ???? >? ? ? > _______________________________________________
    >> ???? >? ? ? > R-sig-meta-analysis mailing list
    >> ???? >? ? ? > R-sig-meta-analysis at r-project.org

    <mailto:R-sig-meta-analysis at r-project.org>

    >> ??? <mailto:R-sig-meta-analysis at r-project.org

    <mailto:R-sig-meta-analysis at r-project.org>>

    >> ???? >? ? ?<mailto:R-sig-meta-analysis at r-project.org

    <mailto:R-sig-meta-analysis at r-project.org>

    >> ??? <mailto:R-sig-meta-analysis at r-project.org

    <mailto:R-sig-meta-analysis at r-project.org>>>

    >> ???? >? ? ? >

    https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis
    >> <https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis>
    >> ???? > ?<https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis
    >> <https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis>>
    >> ???? >? ? ? >
    >> ???? >
    >> ???? >? ? ?--
    >> ???? >? ? ?Michael
    >> ???? > http://www.dewey.myzen.co.uk/home.html
    >> ??? <http://www.dewey.myzen.co.uk/home.html>
    >> ???? >? ? ?<http://www.dewey.myzen.co.uk/home.html
    >> ??? <http://www.dewey.myzen.co.uk/home.html>>
    >> ???? >
    >> ???? >
    >> ???? >
    >> ???? > --
    >> ???? >
    >> ???? > ------------------------------------------
    >> ???? >
    >> ???? > Gladys Barragan-Jason, PhD. ____?Website
    >> ???? > <https://sites.google.com/view/gladysbarraganjason/home
    >> <https://sites.google.com/view/gladysbarraganjason/home>>
    >> ???? >
    >> ???? > Station d'Ecologie Th?orique et Exp?rimentale (SETE)____
    >> ???? >
    >> ???? > CNRS de Moulis____
    >> ???? >
    >> ???? > image.pngimage.png____
    >> ???? >
    >> ???? >
    >> ???? >
    >>
    >> ??? -- ??? Michael
    >> http://www.dewey.myzen.co.uk/home.html
    >> ??? <http://www.dewey.myzen.co.uk/home.html>
    >>
    >

[R-meta] Compiling different design in the same met-analysis

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