[R-meta] Testing multicollinearity between categorical predictors

[Michael Dewey]

Dear Rafael

It is hard to answer here because we do not know what scientific problem 
the referee thinks he or she has spotted which would be solved by such a 
test. Being of a cynical world view I suspect neither does the referee 
and this is a conditioned reflex like Pavlov's dog salivating at the bell.

Are the two moderators of scientific interest to you or are you 
including them so you can say that there is still residual heterogeneity 
even after you did your best to explain it? In the latter case I would 
suggest collinearity is irrelevant.

Michael

On 19/06/2020 13:36, Rafael Rios wrote:
> Dear Wolfgang,
> 
> Thank you for the replay. I also thought about using VIF to evaluate
> multicollinearity, but there is a lot of criticism about the applicability
> of VIF for categorical predictors. There is a variation called GVIF.
> However, since the meta-analysis changes categorical predictors to dummy
> variables, I could not use it in R. I am not sure whether this is the best
> approach. Do you not other methods to evaluate or avoid potential
> multicollinearity among categorical moderators?
> 
> Best wishes,
> 
> Rafael.
> _______________________________________________________
> 
> *Prof. Dr. Rafael Rios Moura*
> 
> *sciencia amabilis *
> Coordenador de Pesquisa e do NEPEE/CNPq
> Laboratório de Ecologia e Zoologia (LEZ)
> UEMG - Unidade Ituiutaba
> 
> ORCID: http://orcid.org/0000-0002-7911-4734
> Currículo Lattes: http://lattes.cnpq.br/4264357546465157
> <http://orcid.org/0000-0002-7911-4734>
> <http://lattes.cnpq.br/4264357546465157>
> <http://lattes.cnpq.br/4264357546465157>Research Gate:
> https://www.researchgate.net/profile/Rafael_Rios_Moura2
> <http://orcid.org/0000-0002-7911-4734>
> Rios de Ciência: https://www.youtube.com/channel/UCu2186wIJKji22ai8tvlUfg
> <http://orcid.org/0000-0002-7911-4734>
> 
> 
> Em sex., 19 de jun. de 2020 às 05:40, Viechtbauer, Wolfgang (SP) <
> wolfgang.viechtbauer using maastrichtuniversity.nl> escreveu:
> 
>> Dear Rafael,
>>
>> I don't know what "testing" for multicollinearity would entail. One could
>> examine the variance inflation factors with vif(). What VIF values are
>> considered "large" is debatable though.
>>
>> Best,
>> Wolfgang
>>
>>> -----Original Message-----
>>> From: Rafael Rios [mailto:biorafaelrm using gmail.com]
>>> Sent: Wednesday, 17 June, 2020 2:28
>>> To: Viechtbauer, Wolfgang (SP); r-sig-meta-analysis using r-project.org
>>> Subject: Testing multicollinearity between categorical predictors
>>>
>>> Dear Wolfgang and All,
>>>
>>> Is there a good method for testing multicollinearity between categorical
>>> predictors in meta-regression? I ran a mixed-effects MLMA using two
>>> categorical predictors and their interaction as moderators, but a Referee
>>> requested a test of multicollinearity. I did not find a good approach to
>>> solve this problem. Thank you in advance.
>>>
>>> Best wishes,
>>> _______________________________________________________
>>>
>>> Prof. Dr. Rafael Rios Moura
>>> sciencia amabilis
>>> Coordenador de Pesquisa e do NEPEE/CNPq
>>> Laboratório de Ecologia e Zoologia (LEZ)
>>> UEMG - Unidade Ituiutaba
>>>
>>> ORCID: http://orcid.org/0000-0002-7911-4734
>>> Currículo Lattes: http://lattes.cnpq.br/4264357546465157
>>> Research Gate: https://www.researchgate.net/profile/Rafael_Rios_Moura2
>>> Rios de Ciência: https://www.youtube.com/channel/UCu2186wIJKji22ai8tvlUfg
>>
> 
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-- 
Michael
http://www.dewey.myzen.co.uk/home.html