[R-meta] specified weights in rma

[James Pustejovsky]

Antonia,

Yes, that's correct. To see this for yourself, try feeding the re-scaled
weights back into the metafor call and compare what you get to your
original results.

James

On Mon, Aug 6, 2018 at 4:58 AM Antonia Sudkaemper <a.sudkaemper using gmail.com>
wrote:

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

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