[R-meta] Dear Wolfgang

Tue, Apr 14, 2020 1:43 PM

Yes, if the effect size measure is the same, one can make such a comparison. Also, there should not be any overlap in the studies included in the two meta-analyses (as otherwise the two estimates are not independent, as assumed by the test). And yes, you don't need sample sizes or tau^2 values or anything else - just the two estimates and their corresponding standard errors. And it doesn't depend on what random effects structure was used in the two meta-analyses -- assuming that the structures used in the two meta-analyses were appropriate for the studies at hand.

Best,
Wolfgang

________________________________________
From: Viechtbauer, Wolfgang (SP)
<wolfgang.viechtbauer at maastrichtuniversity.nl>
Sent: Tuesday, April 14, 2020 7:04 AM
To: Ju Lee <juhyung2 at stanford.edu>; r-sig-meta-analysis at r-project.org <r-
sig-meta-analysis at r-project.org>
Subject: RE: Dear Wolfgang

Dear Ju,

In principle, this might be of interest to you:

http://www.metafor-project.org/doku.php/tips:comp_two_independent_estimates

However, a standardized mean difference is given by (m1-m2)/sd, while a
(log) response ratio is log(m1/m2). I see no sensible way of converting the
former to the later.

Best,
Wolfgang

-----Original Message-----
From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces at r-
project.org]
On Behalf Of Ju Lee
Sent: Monday, 13 April, 2020 22:47
To: r-sig-meta-analysis at r-project.org
Subject: [R-meta] Dear Wolfgang

Dear Wolfgang,

I hope you are doing well.

My research group is currently working on a project where they are trying
to
compare effect sizes generated from their current mixed-effect meta-
analysis
with effect sizes (based on similar response variables) calculated in other
meta-analysis publications.

We are currently using log response ratio and are trying to make some
statement or analysis to compare our grand mean effect sizes with other
studies. In more details, we are examining how herbivorous animal control
plant growth in degraded environment. Now, there is already a meta-analysis
out there that has examined this (in comparable manner) in natural
environment as opposed to our study.

My colleagues want to know if there is a way to make some type of
comparison
(ex. whether responses are stronger in degraded vs. natural environemnts)
between two effect sizes from these different studies using statistical
approaches.
So far what they have from other meta-analysis publication is grand mean
hedges'd and var which they transformed to lnRR and var in hopes to compare
with our lnRR effect sizes.

My view is that this is not possible unless we can have their actual raw
dataset and run a whole new model combining with our original raw dataset.
But I wanted to reach out to you and the community? if there is an
alternative approaches to compare mean effect sizes among different meta-
analysis which are assumed to have used similar approaches in study
selection and models (another issue being different random effect
structures
used in different meta-analysis which may not be very apparent from method
description).

Thank you for reading and I hope to hear from you!
Best,
JU

[R-meta] Dear Wolfgang

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