[R-meta] Dear Wolfgang

[Ju Lee]

Dear Wolfgang,

Thanks for your insights.
I am reaching out to my colleagues to see how they have made such transformation.

In the meantime, based on the information that you have sent, it is possible to compare two different meta-analyses if they are using the same effect size, say lnRR? and this wald-type test can be performed only with grand mean effect sizes and their standard error, without sample sizes or tau value, if I understood correctly?

How would this approach be actually applicable to publications that seemingly used similar mixed-effect models but there is no guarantee that random effect structures are standardized between the two?

Thank you very much!
Best,
JU
________________________________
From: Viechtbauer, Wolfgang (SP) <wolfgang.viechtbauer using maastrichtuniversity.nl>
Sent: Tuesday, April 14, 2020 7:04 AM
To: Ju Lee <juhyung2 using stanford.edu>; r-sig-meta-analysis using r-project.org <r-sig-meta-analysis using 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 using r-project.org]
>On Behalf Of Ju Lee
>Sent: Monday, 13 April, 2020 22:47
>To: r-sig-meta-analysis using 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

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