[R-meta] Threshold values for Cook's Distances and DFBETAS

[Michael Dewey]

Dear Theresa

My feeling is that these diagnostics are better seen as identifying 
values which may benefit from further investigation. If I was concerned 
that they were unduly influential in the model I might try fitting 
leave-one-out models but since those models are essentially data-driven 
they are also only useful in an exploratory sense.

So, even if there is a formula I would be sceptical about its value in 
answering the scientific question.

Michael

On 29/09/2022 21:35, Thölking, Theresa wrote:
> Hello everybody,
> 
> 
> I am trying to apply the outlier and influence diagnostics as described by Viechtbauer and Cheung (2010) on a meta-analysis I conducted, using a four-level random-effects model with 528 included effect sizes. I have calculated the Cook's Distances and DFBETAS in R, using the functions for model diagnostics for rma.mv objects as described here: https://wviechtb.github.io/metafor/reference/influence.rma.mv.html
> 
> 
> However, I don't know how to decide about which studies are influential based on these values. I read the paper by Viechtbauer and Cheung, but I don't quite understand it. Is there some kind of formula to determine the threshold values of CD and DFBETAS for a meta-analytic model with k outcomes? Thanks in advance for your help.
> 
> 
> Best,
> 
> Theresa
> 
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> 
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-- 
Michael
http://www.dewey.myzen.co.uk/home.html