[R-meta] specified weights in rma

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 at r-project.org] On Behalf Of Antonia Sudkaemper
Sent: Monday, 06 August, 2018 11:58
To: James Pustejovsky
Cc: r-sig-meta-analysis at 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 at 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 at 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 Sudk?mper
PhD Candidate in Organizational Psychology/University of Exeter
www.antoniasudkaemper.com
a.sudkaemper at gmail.com