[R-meta] metafor-mota-analysis with between group moderator

Michael Dewey lists at dewey.myzen.co.uk
Fri Dec 1 17:20:18 CET 2017

Dear Matilde

I think you may need to use the so-called bivariate approach


The example there is not identical to your problem but I think it is 
close enough. If Wolfgang does not post saying I am talking rubbish then 
try it and post again with any more queries.


On 01/12/2017 11:43, Matilde Vaghi wrote:
> Dear all,
> I am using metafor to conduct a between group meta-analysis to test if
> there is a difference between groups (controls vs. patients) on the
> continuous independent variable y.
> I need to check the influence of relevant moderator, in particular I obtain
> a between group difference on the variable y and I want to check if the
> finding remains significant after account for the effect of age (if the
> difference in the independent variable y is still difference once adjusted
> for age).
> On the metafor manual, a clear example shows how to assess the effect of a
> moderator (such as latitude) on the variable of interest. However, such
> example refers to the presence of a study-level moderator (each study was
> conducted at a different latitude, therefore one value is associated to
> each study). In my case, each study have two values (i.e, mean age controls
> and mean age patients). Therefore, it is not immediately clear how to adapt
> the following
> Rma(yi, vi, mods=cbind(Latitude), data=df)
> for situations in which there is one moderator variable but two values
> associated to it for each study. I tentatively computed a mean age per
> study ((mean age controls for study 1+ mean age patients for study1)/2;
> ((mean age controls for study 2+ mean age patients for study2)/2 etc) to
> have one value per study but I am not sure this is the best way forward.
> Any advice would be highly appreciated. Many thanks and best wishes,
> Matilde
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