[R-meta] Meta - Bug with REML or small N?

[Michael Dewey]

Dear Jorge

It looks as though the issue is that REML estimates tau^2 to be 
effectively zero whereas DL has a positive estimate. The different ways 
of estimating tau^2 do often differ, sometimes by quite surprising 
amounts. Whether that is related to the smallish number of studies I 
could not say but, at the moment, there does not seem to be evicence of 
anything wrong with the implementation of REML.

Michael

On 21/03/2023 14:57, Jorge Teixeira via R-sig-meta-analysis wrote:
> Hi.
> 
> Let me know if you need me to provide the data for this example. 
> Screenshots in the bottom.
> 
> I ran this MA with REML, and the weight for random and common effects 
> are exactly the same! Never saw anything like this. t2values also don’t 
> look plausible.
> 
> *_#1_*
> vo2 <- metacont(en  , em, esd, cn, cm, csd, study, method.tau = "REML", 
> prediction = TRUE, data = dat_vo2, sm = "MD")
> vo2
> 
> Is this a bug or a particular issue of low number of studies and low 
> sample size?
> 
> *_#2_*
> vo2 <- metacont(en  , em, esd, cn, cm, csd, study, method.tau = "DL", 
> prediction = TRUE, data = dat_vo2, sm = "MD")
> vo2
> 
> I ran this with DL estimator and weights and t2are plausible. I also ran 
> other similar MA using REML and this was all okay.
> 
> #1 using SMD instead of MD also looks fine.
> 
> 
> Thanks,
> Jorge
> 
> 
> *_REML:_*
> 
> image.png
> 
> 
> *_DL:_*
> image.png
> 
> 
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-- 
Michael
http://www.dewey.myzen.co.uk/home.html