Dear Mario,
If you could tell me how to define and interpret I^2 and H^2 for models with
moderators, I may consider implementing these measures for such models.
However, I am not aware of any work that has extended these measures to
meta-regression models.
Best,
--
Wolfgang Viechtbauer
Department of Psychiatry and Neuropsychology
School for Mental Health and Neuroscience
Maastricht University, P.O. Box 616
6200 MD Maastricht, The Netherlands
Tel: +31 (43) 368-5248
Fax: +31 (43) 368-8689
Web: http://www.wvbauer.com
-Original Message-
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org]
On Behalf Of petre...@unina.it
Sent: Sunday, February 20, 2011 13:59
To: r-help@r-project.org
Subject: [R] Help Metafor
Dear Sir, I'm using the Metafor package;
however, introducing moderators, I'm unable to obtain both I^2 (%
of total variability due to heterogeneity) and H^2 (total variability
/ within-study variance). It is possible to obtain I^2 and H^2 also
with moderators?
As example
_Dataset - sqlQuery(channel = 1, select * from [Foglio1$])
names(Dataset) - make.names(names(Dataset))
alloc.a - ifelse(dat$alloc == a, 1, 0)
alloc.b - ifelse(dat$alloc == b, 1, 0)
alloc.c - ifelse(dat$alloc == c, 1, 0)
res-rma.uni(yi, vi, mods=cbind(alloc.a, alloc.b, Year),
measure=GEN, intercept=TRUE, data=dat, slab=Author, subset, add=1/2,
to=only0, vtype=LS, method=REML, weighted=TRUE, knha=FALSE,
btt=c(2,3))
print (res)
Mixed-Effects Model (k = 22; tau^2 estimator: REML)
tau^2 (estimate of residual amount of heterogeneity): 0.7810 (SE = 0.2924)
tau (sqrt of the estimate of residual heterogeneity): 0.8838
Test for Residual Heterogeneity:
QE(df = 18) = 223.3159, p-val .0001
Test of Moderators (coefficient(s) 2,3):
QM(df = 2) = 0.8251, p-val = 0.6620
Model Results:
estimate se zval pval ci.lb ci.ub
intrcpt -135.3524 54.4487 -2.4859 0.0129 -242.0700 -28.6349 *
alloc.a -0.3836 0.4529 -0.8469 0.3971 -1.2713 0.5042
alloc.b -0.3656 0.5529 -0.6613 0.5084 -1.4493 0.7180
Year 0.0673 0.0273 2.4677 0.0136 0.0139 0.1208 *
Many thanks
_
Mario Petretta
Dipartimento di Medicina Clinica Scienze Cardiovascolari e Immunologiche
Facoltà di Medicina e Chirurgia
Università di Napoli Federico II
081 - 7462233
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