[R-meta] Questions about Omnibus tests
Dear Wolfgang, Thank you for the clarification! There are just a few more questions that I hope you may help me. I used your script to calculate I? and found a high heterogeneity in my model (86.63%). #I?: http://www.metafor-project.org/doku.php/tips:i2_multilevel_multivariate W <- diag(1/h_mc$vzf) X <- model.matrix(model1) P <- W - W %*% X %*% solve(t(X) %*% W %*% X) %*% t(X) %*% W 100 * sum(meta$sigma2) / (sum(meta$sigma2) + (meta$k-meta$p)/sum(diag(P))) Do you have suggestions on how to handle with high heterogeneity among effect sizes? How may I conduct sensitivity tests in a multilevel meta-analysis using metafor? I identified (using a funnel plot) and removed outliers to reduce the heterogeneity and redo the model. Then, I compared the results of both models to evaluate if there is any discrepancies. Is this approach suitable to evaluate potential bias in the results? Or are there better alternatives? Best wishes, Rafael. __________________________________________________________ Dr. Rafael Rios Moura *scientia amabilis* Behavioral Ecologist, PhD Postdoctoral Researcher Universidade Estadual de Campinas (UNICAMP) Campinas, S?o Paulo, Brazil Curr?culo Lattes: http://lattes.cnpq.br/4264357546465157 ORCID: http://orcid.org/0000-0002-7911-4734 Research Gate: https://www.researchgate.net/profile/Rafael_Rios_Moura2 <http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4244908A8> Em qui, 8 de nov de 2018 ?s 13:48, Viechtbauer, Wolfgang (SP) < wolfgang.viechtbauer at maastrichtuniversity.nl> escreveu:
As for the model to use: In general, you want to use: ~1|studyID/effectsizeID Using list(~1|effectsizeID, ~1|studyID) may be correct if effectsizeID is unique for every row. This is essentially a question of 'explicit' versus 'implict' nesting. See also: https://stat.ethz.ch/pipermail/r-sig-meta-analysis/2018-July/000896.html Best, Wolfgang -----Original Message----- From: Rafael Rios [mailto:biorafaelrm at gmail.com] Sent: Sunday, 04 November, 2018 0:32 To: Viechtbauer, Wolfgang (SP) Cc: Michael Dewey; r-sig-meta-analysis at r-project.org Subject: Re: [R-meta] Questions about Omnibus tests Dear Wolfgang, Could you please help me again with new questions? Should I build model1 rather than model2 to control for the dependency among studyID and effectsizeID? model1=rma.mv(zf, vzf, mods=~mate_choice, random=list(~1|studyID/effectsizeID, ~1|species1), data = h_mc) model2=rma.mv(zf, vzf, mods=~mate_choice, random=list(~1|effectsizeID, ~1|studyID, ~1|species1), data = h_mc) I used your script to calculate I? and found a high heterogeneity in my model (86.63%). #I?: http://www.metafor-project.org/doku.php/tips:i2_multilevel_multivariate W <- diag(1/h_mc$vzf) X <- model.matrix(model1) P <- W - W %*% X %*% solve(t(X) %*% W %*% X) %*% t(X) %*% W 100 * sum(meta$sigma2) / (sum(meta$sigma2) + (meta$k-meta$p)/sum(diag(P))) Do you have suggestions on how to handle with high heterogeneity among effect sizes? How may I conduct sensitivity tests in a multilevel meta-analysis using metafor? I identified (using a funnel plot) and removed outliers to reduce the heterogeneity and redo the model. Is this approach suitable to evaluate potential bias in results? Or are there better alternatives? Best wishes, Rafael.
__________________________________________________________ Dr. Rafael Rios Moura scientia amabilis Behavioral Ecologist, PhD Postdoctoral Researcher Universidade Estadual de Campinas (UNICAMP) Campinas, S?o Paulo, Brazil Curr?culo Lattes: http://lattes.cnpq.br/4264357546465157 ORCID: http://orcid.org/0000-0002-7911-4734 Research Gate: https://www.researchgate.net/profile/Rafael_Rios_Moura2