Dear R community,

 

I'm using the ,metafor'-package by Wolfgang Viechtbauer (Version: 0.5-5) to
calculate random-effects meta-analyses using Correlations and Sample Sizes
as the raw data. 

(By the way: Really a nice piece of work, Wolfgang! Thanks heaps.)

 

I specified the "rma.uni' function so that it looks like this:

MAergebnis<-rma.uni(ri=PosOutc, ni=N,

                mods=NULL,

                data=dm, intercept=TRUE, slab=c(dm$Article, dm$StudyNo),

                subset=NULL, measure="ZCOR", add=1/2, to="only0",
vtype="LS",

                method="DL", weighted=TRUE, level=95, digits=4, btt=NULL,

                tau2=NULL, knha=FALSE, control=list())

 

With PosOutc being the column containing the raw correlations and N being
the column with the sample sizes.

 

I assume that this will imply that 

a) although the 'tau2' value is set to NULL, still a random-effects analysis
is calculated

b) the raw correlation coefficients are transformed to fisher-z-values

c) the according variances of the fisher-z-values are calculated from the
sample sizes

d) these calculated z-values and sample sizes are then used to calculate
summary effect and confidence interval limits

e) the resulting object contains z-values and not raw correlations

 

Now, the problem is: 

How do I get the calculated results back into the form of raw correlation
coefficients? (In order to report them in an article.)

I see two cases, where this might be relevant:

 

A) When reporting numeric results:

I tried the following:

    print.rma.uni(MAergebnis, transf="transf.ztor")

but then noticed that the following will bring up the same result:

    print.rma.uni(MAergebnis)

(When using the "z2r" and "r2z" functions out of the "psychometric"-package
on the separate numbers, the values change, so it can't simply be a matter
of rounding.)

 

B) When drawing a forest plot:

    forest(MAergebnis, ., transf="transf.ztor", .)

should to the trick, right?

 

Does anyone have any experience or greater insight knowledge regarding this
little problem? 

Best regards

Sebastian

 

 

 


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