[R-meta] tau^2 for multilevel models

[Alexandra Voce]

Dear mailing list,

If I have a multilevel model, say:

dat <- get(data(dat.bcg))
dat <- escalc(measure="RR", ai=tpos, bi=tneg, ci=cpos, di=cneg, data=dat.bcg)

example <- rma.mv(yi, vi, random = ~ 1 | alloc/trial, data=dat)

Is the sum of the sigma^2 values in this model equivalent to tau^2 that would be calculated in a more general random effects model, e.g..

example2 <- rma(yi, vi, data=dat)

By equivalent, I mean is it correct to state that the sum of sigma^2 values in a multilevel model reflects the estimated amount of total heterogeneity? Is there any reason it could be considered incorrect to detail this value (sigma^2_between + sigma^2_within) as tau2?

Thank you,
Alexandra

Dr Alexandra Voce
Research Analyst
Australian Institute of Criminology
E: Alexandra.voce using aic.gov.au<mailto:Alexandra.voce using aic.gov.au>
W: www.aic.gov.au


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