[R] Help Metafor

[Viechtbauer Wolfgang (STAT)]

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-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> On Behalf Of petretta at unina.it
> Sent: Sunday, February 20, 2011 13:59
> To: r-help at 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