[R-meta] rma.mv only for better SEs
Simon Harmel
@|m@h@rme| @end|ng |rom gm@||@com
Mon Jan 31 21:14:12 CET 2022
This is very helpful, thank you so very much.
Simon
ps. This may be loosely relevant but in ordinary multilevel models, we
don't use weights, but still random-effects' structures do have a bearing
on the fixed effect estimates. So, aside from weights, something else from
random-effects must have an impact on fixed-effect magnitude.
On Mon, Jan 31, 2022 at 2:04 PM Viechtbauer, Wolfgang (SP) <
wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:
> Right, sorry, that was a typo.
>
> Best,
> Wolfgang
>
> >-----Original Message-----
> >From: Simon Harmel [mailto:sim.harmel using gmail.com]
> >Sent: Monday, 31 January, 2022 19:29
> >To: Viechtbauer, Wolfgang (SP)
> >Cc: R meta
> >Subject: Re: [R-meta] rma.mv only for better SEs
> >
> >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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