<html><head></head><body><div style="font-family: Verdana;font-size: 12.0px;"><div>Dear All,</div>
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<div>I have a question concerning the combination/pooling of means. Since most of my studies are correlated I deceided to use robust variance estimation method to do this. So metamean function in meta was out because of this. So I used robumeta. Since in some cases I had negative values I deceided to use log transformed means for pooling. My problem is that the estimates look reasonable now with robumeta but the heterogeneity parameters(e.g. Tau, I²) are all estimated with zero. This is strange. Does anybody know why that is?</div>
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<div>Regards,</div>
<div>Tobias Saueressig</div>
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<div>Reproducible example:</div>
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<div>#Example</div>
<div> Author <-c("Carboch et al. (2019)","Stare et al. (2015)","Mackie (2013)","Hornery et al. (2007)",<br/>
"Takahashi et al. ( 2006)","Morante et al. (2005)","O'Donoghue, P. and Ingram, B. (2001)",<br/>
"O'Donoghue, P. and Ingram, B. (2001)")<br/>
<br/>
Mean<-c(5.93,4.40,6.42,6.70,5.10,6.40,5.70,4.90)<br/>
SD<-c(0.67,1.73,1.27,2.20,5.19,1.40,1.00,1.40)<br/>
N<-c(7,5,9,17,16,12,24,35)<br/>
SEM<-c(0.25,0.77,0.42,0.53,1.30,0.40,0.20,0.24)<br/>
LogMean<-c(1.78,1.48,1.86,1.90,1.63,1.86,1.74,1.59)<br/>
LogMean_SEM<-c(1.50,3.40,2.72,3.57,6.62,2.59,1.16,1.16)<br/>
<br/>
dat<-data.frame(Author,Mean,SD,N,SEM,LogMean,LogMean_SEM)<br/>
<br/>
#Formulas used<br/>
#SEM<-SD/sqrt(N)<br/>
#LogMean<-log(Mean)<br/>
#LogMean_SEM<-SD^2/(N*Mean^2) => taken from metamean function in meta<br/>
<br/>
#normalscale<br/>
res <- robu(formula = Mean ~ 1, data = dat,<br/>
studynum = Author, var.eff.size =SEM,<br/>
rho = .8, small = TRUE, modelweights="CORR")<br/>
res<br/>
<br/>
#logscale<br/>
res1 <- robu(formula = LogMean ~ 1, data = dat,<br/>
studynum = Author, var.eff.size = LogMean_SEM,<br/>
rho = .8, small = TRUE, modelweights="CORR")<br/>
res1<br/>
<br/>
#backtransformed results from log scale<br/>
round(exp(c(res1$reg_table$b.r[[1]],res1$reg_table$CI.L[[1]],res1$reg_table$CI.U[[1]])),2) <br/>
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