[R-meta] Help with understanding the meta objecct

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