[R-meta] rma.mv only for better SEs

[Simon Harmel]

Sure, but didn't you by any chance mean to say:
"The random effects structure determines the weight matrix, which in turn
affects the estimates of the **fixed effects**".

On Mon, Jan 31, 2022 at 12:23 PM Viechtbauer, Wolfgang (SP) <
wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:

> The random effects structure determines the weight matrix, which in turn
> affects the estimates of the random effects.
>
> Best,
> Wolfgang
>
> >-----Original Message-----
> >From: Simon Harmel [mailto:sim.harmel using gmail.com]
> >Sent: Monday, 31 January, 2022 18:29
> >To: Viechtbauer, Wolfgang (SP)
> >Cc: R meta
> >Subject: Re: [R-meta] rma.mv only for better SEs
> >
> >I have done it, and in my case the results differ. But my point was, is my
> >explanation regarding why they differ accurate?
> >
> >On Mon, Jan 31, 2022 at 11:24 AM Viechtbauer, Wolfgang (SP)
> ><wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:
> >Just try it out and you will see what happens.
> >
> >Best,
> >Wolfgang
> >
> >>-----Original Message-----
> >>From: Simon Harmel [mailto:sim.harmel using gmail.com]
> >>Sent: Monday, 31 January, 2022 18:21
> >>To: Viechtbauer, Wolfgang (SP)
> >>Cc: R meta
> >>Subject: Re: [R-meta] rma.mv only for better SEs
> >>
> >>Thank you, Wolfgang. I asked this, because I noticed applying RVE to an
> rma.mv()
> >>model has no bearing on the estimates of fixed effects themselves, and
> just
> >>modifies their SEs.
> >>
> >>So, I wondered if the same rule, at least "in principle", should apply
> when we
> >go
> >>from rma() to rma.mv().
> >>
> >>But is there a principle regarding how random effects affect the fixed
> effects?
> >>
> >>For instance, in:
> >>
> >>1- rma.mv(y ~ 1, random = ~ 1|study/obs), the overall average only
> represents
> >the
> >>average of study-level effects.
> >>
> >>But, in:
> >>
> >>2- rma.mv(y ~ 1, random = ~ 1|study/outcome/obs), the overall average
> represents
> >>the average of study-level effects additionally affected by the
> outcome-level
> >>effects within them.
> >>
> >>And thus, 1- and 2- may give different overall averages, right?
> >>
> >>Simon
> >>
> >>On Mon, Jan 31, 2022 at 11:00 AM Viechtbauer, Wolfgang (SP)
> >><wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:
> >>Generally, two models with different random effects structures will also
> give
> >you
> >>different estimates of the fixed effects (unless the estimates of the
> >>variance/covariance components happen to be such that the two models
> collapse
> >>down to the same structure).
> >>
> >>Best,
> >>Wolfgang
> >>
> >>>-----Original Message-----
> >>>From: R-sig-meta-analysis [mailto:
> r-sig-meta-analysis-bounces using r-project.org] On
> >>>Behalf Of Simon Harmel
> >>>Sent: Monday, 31 January, 2022 17:49
> >>>To: R meta
> >>>Subject: [R-meta] rma.mv only for better SEs
> >>>
> >>>Hello List Members,
> >>>
> >>>Reviewing the archived posts, my understanding is that my studies can
> >>>produce multiple effects, so I should use rma.mv() not rma().
> >>>
> >>>Also, I understand rma.mv() ensures that I get more accurate SEs for my
> >>>fixed effects relative to rma().
> >>>
> >>>BUT does that also mean that, by definition, rma.mv() should have no
> >>>bearing on the magnitude of the fixed effects themselves and only
> modifies
> >>>their SEs relative to rma()?
> >>>
> >>>Thank you,
> >>>Simon
>

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