-----Original Message-----
From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces at r-project.org]
On Behalf Of Tobias Saueressig
Sent: Monday, 17 August, 2020 12:03
To: r-sig-meta-analysis at r-project.org
Subject: [R-meta] Data Extraction
Hello,
I have a problem to extract data from one study.? I want to calculate hedges
g.
I have the following information (2 groups):
Between-group change score from baseline to follow-up (9?months) is?1.8(-
5.7,9.3) (mean and 95%CI) and p-value 0.64
Sample size is n1 = 30; n2 = 36?(two group RCT).
Link:?https://linkinghub.elsevier.com/retrieve/pii/S1063458420309882?(TABLE
2 HOOS ADL)
I would do it the following way:
Calculate a SD for both group from the CI. _> SE = (Upper limit-lower
limit)/t-statistic (~2) => SD = SE/squ(1/n1?+ 1/n2)
Then g = d = MD/SD
g* = (1-3/(4*(n1+n2)-9) * g
e.g.
SE = (9.3+5.7)/1.99 = 7.54 => SD = 7.54/squ(1/30+1/36) = 7.54/0.25 = 30.16
g = 1.8/30.16 = 0.06
g* = 0.06 * (1-3/255) = 0.06 * 0.99 = 0.0594
Is that correct?
Best regards
Tobias