[R-meta] Welcome to the "R-sig-meta-analysis" mailing list

Anne-Wil Kruijt mail at awkruijt.nl
Mon Oct 16 17:18:49 CEST 2017

Dear all,

Thank you, professor Viechtbauer, for referring me to this list. 

Delving into metafor’s mechanics I noticed that when ‘method = “MN” ‘ is specified in escalc(), its calculation of sampling variance (vi) is “vi <- sdi^2/ni”. I wondered why there is no option to use the(/a?) unbiased estimator “vi <- sdi^2/ni-1”. I’m considered to bypass the escalc step and ‘manually’ compute vi as sdi^2/ni-1 – but I’m hesitant because it isn’t an option in escalc() (when method = “MN”, i.e. when obtaining the ‘raw mean difference’ for input as yi). Does anyone have any insights to share on why it is or is not a good idea to use the ‘unbiased estimator’ in the context of a REML MA on raw mean difference values? 

All best,


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