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

-----Original Message-----
From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces at r-project.org] On
Behalf Of Michael Dewey
Sent: Friday, 30 September, 2022 11:08
To: Th?lking, Theresa; r-sig-meta-analysis at r-project.org
Subject: Re: [R-meta] Threshold values for Cook's Distances and DFBETAS

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, Th?lking, 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