<html><head></head><body><div style="font-family: Verdana;font-size: 12.0px;"><div>Hello,</div>
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<div>I have one more question on data extraction:</div>
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<div>I have two groups n1 = 43 and n2 = 41</div>
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<div>Baseline values (mean, SD): 48 (15) and 47.3 (19.4)</div>
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<div>Change within-group (mean, 95%CI): 29.7 (24.7 to 34.7) and 26.7 (21.6 to 31.8)</div>
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<div>Difference between group changes (meandiff, 95%CI, pvalue): −3.0 (−10.1 to 4.1) 0.4087</div>
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<div>I would do the following:</div>
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<div>SDchange1 <- (sqrt(43)*(34.7-24.7))/(2*qt(.975, df=43-1))</div>
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<div>SDchange2 <- (sqrt(44)*(31.8-21.6))/(2*qt(.975, df=43-1))</div>
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<div><span lang="EN-US" style="font-size:9.0pt"><span style="line-height:107%"><span style="font-family:"Verdana",sans-serif"><span style="color:black">Assume: SD of change scores = SD * sqrt(2*(1-r)) with r =0.9</span></span></span></span></div>
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<div><span lang="EN-US" style="font-size:9.0pt"><span style="line-height:107%"><span style="font-family:"Verdana",sans-serif"><span style="color:black">SD1prepost <- (</span></span></span></span>(sqrt(43)*(34.7-24.7))/(2*qt(.975, df=43-1)))/sqrt(0.2)</div>
<div>SD1prepost</div>
<div><span lang="EN-US" style="font-size:9.0pt"><span style="line-height:107%"><span style="font-family:"Verdana",sans-serif"><span style="color:black">SD2prepost <- </span></span></span></span>(sqrt(44)*(31.8-21.6))/(2*qt(.975, df=41-1))/sqrt(0.2)</div>
<div><span lang="EN-US" style="font-size:9.0pt"><span style="line-height:107%"><span style="font-family:"Verdana",sans-serif"><span style="color:black">SD2prepost</span></span></span></span></div>
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<div>require(metafor)</div>
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<div>postmean1= 77.7 and postmean2 = 74</div>
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<div><span lang="EN-US" style="font-size:9.0pt"><span style="line-height:107%"><span style="font-family:"Verdana",sans-serif"><span style="color:black">summary(escalc(measure="SMD", m1i=77.7, sd1i=</span></span></span></span>SD1prepost<span lang="EN-US" style="font-size:9.0pt"><span style="line-height:107%"><span style="font-family:"Verdana",sans-serif"><span style="color:black">, m2i=74, sd2i=SD2prepost, n1i=43, n2i=41))</span></span></span></span></div>
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<div>Thanks in advance.</div>
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<div>Tobias</div></div></body></html>