[R-meta] Subgroup analyses

[David Cicchetti]

Dear Philippe,

Thank you for the links, they seem to solve my issue.

David

Quoting Philippe Tadger <philippetadger using gmail.com>:

> Dear David
>
> You can see answer to your question here:
>
> https://www.metafor-project.org/doku.php/tips:models_with_or_without_intercept  
> <https://www.metafor-project.org/doku.php/tips:models_with_or_without_intercept>
>
> https://stats.stackexchange.com/questions/191144/interpreting-intercept-only-meta-analysis-model-when-effect-size-is-raw-mean  
> <https://stats.stackexchange.com/questions/191144/interpreting-intercept-only-meta-analysis-model-when-effect-size-is-raw-mean>
>
> https://stat.ethz.ch/pipermail/r-sig-meta-analysis/2018-May/000818.html  
> <https://stat.ethz.ch/pipermail/r-sig-meta-analysis/2018-May/000818.html>
>
> I would not substract the intercept, in most of the cases is a  
> strong assumption.
>
> On 25/08/2021 12:55, David Cicchetti wrote:
>>
>> Dear list members,
>>
>> I am trying to run subgroup analyses in my meta analysis. I have  
>> the issue that I do not know whether I should include an intercept  
>> or not, meaning whether I should do mods = ~ Coil.Type (with  
>> intercept) or mods = ~ Coil.Type - 1 (without intercept).
>>
>> From what I know so far we can leave out the intercept if for x = 0  
>> -> y = 0. Unfortunately I don't think that logic applies here. My  
>> variables (as for example Coil Type) do not have a 'zero'  
>> condition, it compares for example Coil A with Coil B.
>> If I want to write down the values as a table, I cannot do that  
>> well when including the intercept because then the estimate,  
>> standard error and CI are from the difference to the intercept and  
>> not from the level itself.
>>
>> Since the Moderator tests become more easily significant when  
>> excluding the intercept, I was hesitant to do so. Therefore I would  
>> be thankful if anyone could clear me up on when/if I am allowed to  
>> get rid of the Intercept in my case.
>>
>> Thanks in advance.
>>
>> Best,
>> David
>>
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> -- 
> Kind regards/Saludos cordiales
> *Philippe Tadger*
> ORCID <https://orcid.org/0000-0002-1453-4105>, Reseach Gate  
> <https://www.researchgate.net/profile/Philippe-Tadger>
> Phone/WhatsApp: +32498774742