metafor escalc(measure="SMCC")
Dear all, I use R 3.0 for Windows. I ask how escalc(measure="SMCC") [metafor package] mathematically calculate yi and vi when only change score and SD change score are provided. I used the example (repoted below) posted by Qiang Yue at: http://r.789695.n4.nabble.com/using-metafor-for-meta-analysis-of-before-after-studies-escalc-SMCC-td4667233.html but it is unclear for me the formula used to derive y1 and v1. I read the documentation of metafor package and it is all very well described, but I ask if possible for the formula used by escalc(measure="SMCC") to mathematically calculate yi and vi. Unfortunatel, I have no free access to the paper quoted in metafor package. Beginning example: fMRS author year n mean_r sd_r mean_s sd_s r 1 Tom 2006 9 0 0 0.12 0.03 0 0 2 Jack 2012 6 0 0 0.23 0.05 0 0 3 Zhu 2013 8 0 0 0.18 0.05 0 0
dat_SMCC=escalc(measure="SMCC",data=fMRS,ni=n,m1i=mean_s,m2i=mean_r,sd1i=sd_s,sd2i=sd_r,ri=r
,append=TRUE)
dat_SMCC
author year n mean_r sd_r mean_s sd_s r yi vi 1 Tom 2006 9 0 0 0.12 0.03 0 3.6108 0.8354 2 Jack 2012 6 0 0 0.23 0.05 0 3.8674 1.4131 3 Zhu 2013 8 0 0 0.18 0.05 0 3.1975 0.7640 Sincerely
Mario Petretta Department of Translational Medical Sciences Naples University Federico II Italy