[R-meta] Correcting Hedges' g vs. Log response ratio in nested studies

[Viechtbauer, Wolfgang (NP)]

Dear Yuhang,

I haven't looked deeply into this, but an immediate thought I have is that for SMDs, you divide by some measure of variability within the groups. If that measure of variability is affected by your study design, then this will also affect the SMD value. On the other hand, this doesn't have any impact on LRRs since they are only the (log-transformed) ratio of the means.

Best,
Wolfgang

> -----Original Message-----
> From: R-sig-meta-analysis <r-sig-meta-analysis-bounces using r-project.org> On Behalf
> Of Yuhang Hu via R-sig-meta-analysis
> Sent: Thursday, November 2, 2023 05:42
> To: R meta <r-sig-meta-analysis using r-project.org>
> Cc: Yuhang Hu <yh342 using nau.edu>
> Subject: [R-meta] Correcting Hedges' g vs. Log response ratio in nested studies
>
> Hello All,
>
> I know that when correcting Hedges' g (i.e., bias-corrected SMD, aka "g")
> in nested studies, we have to **BOTH** adjust our initial "g" and its
> sampling variance "vi_g"
> (https://ies.ed.gov/ncee/wwc/Docs/referenceresources/WWC-41-Supplement-
> 508_09212020.pdf).
>
> But when correcting Log Response Ratios (LRR) in nested studies, we have to
> **ONLY** adjust its initial sampling variance "vi_LRR" but not "LRR" itself
> (https://stat.ethz.ch/pipermail/r-sig-meta-analysis/2021-October/003486.html).
>
> I wonder why the two methods of correction differ for Hedge's g and LRR?
>
> Thanks,
> Yuhang