[R-meta] The correct formula for variance when using SMCR

[Colin Tredoux]

Dear Wolfgang Viechtbauer, or other parties who may be able to comment:

Thanks so much for your very useful R package, Metafor.

One question, if I may ask it, concerns a section in the code file escalc.R lines 1878 to 1883, for computing SMCR
(https://github.com/wviechtb/metafor/blob/master/R/escalc.r)

### large sample approximation to the sampling variance (using corrected (!) equation from Borenstein, 2009)
               if (vtype[i] == "LS2")
                  vi[i] <- cmi[i]^2 * (2*(1-ri[i])/ni[i] + di[i]^2 / (2*ni[i]))
                  #vi[i] <- cmi[i]^2 * 2*(1-ri[i]) * (1/ni[i] + di[i]^2 / (2*ni[i])) # as in  Borenstein (2009) but this is incorrect

            }

I am wondering which article by Borenstein you are referring to?  The chapter in the second edition of the Handbook?
Has it been corrected in the third edition?
I see that there might be an inconsistency between the formula reported by Becker (1988) and by Borenstein, but am wondering if that is because it is not an SMCR he outlines there.

Bottom line - if you have a moment to indicate what the mistake is, I would appreciate that.  I will be using Metafor to run a meta-analysis very soon, and am considering using SMCR as the effect size, but am a little concerned about potential formula issues.

--
Colin Tredoux


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