Message-ID: <2ef86f3be8294f0b8d4f8df6672bee1a@uniklinik-freiburg.de>
Date: 2023-07-20T16:09:36Z
From: Dr. Gerta Rücker
Subject: [R-meta] Help with understanding the meta objecct
In-Reply-To: <c59f84d3-3bb8-06b3-20d2-30f5d60bdfc5@tu-dresden.de>
Dear Jan,
As seen in the output, correlation coefficients (r) are transformed for meta-analysis using Fisher's z-transformation. That is, they are not directly pooled, but transformed by
z = 0.5*log((1 + r)/(1 - r))
with inverse transformation r = (exp(2*z) - 1)/ (exp(2*z) + 1). Using the example given in the help file of metacor()
m1 <- metacor(c(0.85, 0.7, 0.95), c(20, 40, 10))
you obtain the z-transformed pooled effect size from the metacor list object by
z <- m1$TE.random
and may backtransform it by
r <- (exp(2*z) - 1)/ (exp(2*z) + 1)
which gives 0.8438764 as in the print output or the forest plot.
Best,
Gerta
UNIVERSIT?TSKLINIKUM FREIBURG
Institute for Medical Biometry and Statistics
Dr. Gerta R?cker
Guest Scientist
Stefan-Meier-Stra?e 26 ? 79104 Freiburg
gerta.ruecker at uniklinik-freiburg.de
https://www.uniklinik-freiburg.de/imbi-en/employees.html?imbiuser=ruecker
-----Urspr?ngliche Nachricht-----
Von: R-sig-meta-analysis <r-sig-meta-analysis-bounces at r-project.org> Im Auftrag von Jan Pohl via R-sig-meta-analysis
Gesendet: Donnerstag, 20. Juli 2023 14:46
An: r-sig-meta-analysis at r-project.org
Cc: Jan Pohl <jan.pohl at tu-dresden.de>
Betreff: [R-meta] Help with understanding the meta objecct
Good day everybody,
I have a question about accessing the metacor object in the meta
package. I have a meta-analysis where before now I just used the values
as seen in the output, e.g., in this example I reported 0.3369 as my
effect size:
Number of studies combined: k = 88
Number of observations: o = 5306
??????????????????????? COR??????????? 95%-CI???? z? p-value
Fixed effect model?? 0.3301 [ 0.3052; 0.3544] 24.35 < 0.0001
Random effects model 0.3369 [ 0.2390; 0.4281]? 6.43 < 0.0001
Prediction interval???????? [-0.5375; 0.8622]
Now I want to create some custom plots where I want to use values like
the ES from this object. However, my problem is that I cannot find the
ES value in the list. So, I am wondering if the value is somewhow
transformed or if I misunderstood something?
I would greatly appreciate if somebody could help me shed light on this
problem. Thank you very much already in advance.
Kind regards,
Jan
--
Jan Pohl
Technische Universit?t Dresden
Faculty of Psychology
Zellescher Weg 19
01069 Dresden
Jan.Pohl at tu-dresden.de