[R-meta] Testing multicollinearity between categorical predictors

[Viechtbauer, Wolfgang (SP)]

I am not sure I fully understand. Are you saying that the two moderators have two levels each?

Best,
Wolfgang

>-----Original Message-----
>From: Rafael Rios [mailto:biorafaelrm using gmail.com]
>Sent: Friday, 19 June, 2020 15:02
>To: Michael Dewey
>Cc: Viechtbauer, Wolfgang (SP); r-sig-meta-analysis using r-project.org
>Subject: Re: [R-meta] Testing multicollinearity between categorical
>predictors
>
>Dear Michael,
>
>Thank you for the reply. I am evaluating the biases arising from pooling
>samples from different populations and periods on the average effect size.
>Therefore, I included both pooling practices, and their interaction as
>moderators. Each practice has two levels (yes and no).
>
>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
>Research Gate: https://www.researchgate.net/profile/Rafael_Rios_Moura2
>Rios de Ciência: https://www.youtube.com/channel/UCu2186wIJKji22ai8tvlUfg
>
>Em sex., 19 de jun. de 2020 às 09:50, Michael Dewey
><lists using dewey.myzen.co.uk> escreveu:
>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