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

Hi Gladys,

Note that separate meta-analyses is not the same as subgroup analysis. If
you do a subgroup analysis (in the Cochrane sense), you have design as a
moderator and obtain a treatment-design interaction test, which you don't
get if conducing separate analyses. Therefore I would prefer to present all
in one.

Best,

Gerta
Am 04.05.2021 um 11:17 schrieb Gladys Barragan-Jason:

Hi all,
Thanks a lot for your responses.
Actually, I did not specify it before but I am using the rma.mv function
since I can have several estimates from several studies of the same lab
(random=~1|lab/study/estid). Following your recommendations, I checked
whether the type of design had a significant effect on effect sizes and
actually it didn't except for one specific type of intervention in which I
do not have that much data:  3 papers for each design containing 7 and 4
effect sizes respectively. In this case, meta-analysis of overall estimates
is non-significant while when computing them separately, one is significant
(control vs. treatment groups) while the other is not (pre- vs. post
treatment).
I do think that would make sense to present the overall meta-analysis as
well as the two designs separately ? In any case, we would need more data
to conclude for sure.
Best,
Gladys

Le lun. 3 mai 2021 ? 20:18, Viechtbauer, Wolfgang (SP) <
wolfgang.viechtbauer at maastrichtuniversity.nl> a ?crit :

Agree, but I also want to point to this:

https://www.metafor-project.org/doku.php/tips:computing_adjusted_effects

It discusses the concept of computing adjusted effects, which may be what
you are looking for, Gladys. However, as noted at the end, some may
question the usefulness and interpretability of such an estimate.

Best,
Wolfgang

-----Original Message-----
From: R-sig-meta-analysis [mailto:

r-sig-meta-analysis-bounces at r-project.org] On

Behalf Of Dr. Gerta R?cker
Sent: Monday, 03 May, 2021 20:09
To: Gladys Barragan-Jason
Cc: R meta
Subject: Re: [R-meta] Compiling different design in the same met-analysis

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

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Gladys Barragan-Jason, PhD.  Website
<https://sites.google.com/view/gladysbarraganjason/home>

Station d'Ecologie Th?orique et Exp?rimentale (SETE)

CNRS de Moulis

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