[R-meta] specified weights in rma

[Antonia Sudkaemper]

Aw, great, that is very useful, thanks a lot! All the best, Antonia

On 6 August 2018 at 14:38, Viechtbauer, Wolfgang (SP) <
wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:

> The weights are only rescalled to percentages when using weights().
> Internally, the unscalled weights are used for the computations.
>
> If you want to see the unscalled weights, you could use:
>
> diag(weights(meta, type="matrix"))
>
> weights(meta, type="matrix") gives the whole weight matrix (which is
> diagonal for models fitted with rma()) without any rescalling and then
> diag() gives you just the diagonal.
>
> Best,
> Wolfgang
>
> -----Original Message-----
> From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-
> bounces using r-project.org] On Behalf Of Antonia Sudkaemper
> Sent: Monday, 06 August, 2018 11:58
> To: James Pustejovsky
> Cc: r-sig-meta-analysis using r-project.org
> Subject: Re: [R-meta] specified weights in rma
>
> Hello James,
>
> thank you very much for your reply, that was very useful - I hadn't
> realised the numbers were re-scaled versions of the ones I had specified!
>
> If I understand this correctly then, the re-scaling does not effect my
> results, i.e. mean, confidence intervals, p-value?
>
> Thank you very much.
>
> All the best, Antonia
>
> On 3 August 2018 at 14:55, James Pustejovsky <jepusto using gmail.com> wrote:
>
> > Antonia,
> >
> > The code looks correct to me, and it looks like it is producing the
> > weighted average just as you specified:
> >
> >     mean_effect <- weighted.mean(effect, w = weight)
> >     all.equal(mean_effect, as.numeric(meta$b), check.attributes = FALSE)
> >
> > Also, note that the output of weights() is re-scaled to sum to 100, which
> > is why it does not agree with the inputted weights:
> >
> >     (rma_wt <- weights(meta))
> >     sum(rma_wt)
> >     100 * weight / sum(weight)
> >     all.equal(rma_wt, 100 * weight / sum(weight), check.attributes =
> FALSE)
> >
> > Cheers,
> > James
> >
> >
> >
> > On Fri, Aug 3, 2018 at 7:10 AM Antonia Sudkaemper <
> a.sudkaemper using gmail.com>
> > wrote:
> >
> >> Hello all,
> >>
> >> I am trying to run a meta-analysis with specified weights, but even
> though
> >> the code seems right the analysis seems to apply the default weights
> >> rather
> >> than the ones I specify - is there something wrong with the code?
> >>
> >> effect = c(2.46, 3.11, 3.93)
> >> error = c(0.44, 0.38, 0.57)
> >> weight = c(5.16, 6.70, 3.05)
> >> study<-c("Study1", "Study2", "Study3")
> >>
> >> summary(meta <- rma(yi=effect, sei=error, weights=weight, slab=study))
> >> weights(meta)
> >>
> >>
> >> Thank you very much for your help.
> >>
> >> All the best, Antonia
> >>
> >> --
> >> Antonia Sudkämper
> >> PhD Candidate in Organizational Psychology/University of Exeter
> >> www.antoniasudkaemper.com
> >> a.sudkaemper using gmail.com
>



-- 
Antonia Sudkämper
PhD Candidate in Organizational Psychology/University of Exeter
www.antoniasudkaemper.com
a.sudkaemper using gmail.com

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