I have several RCT pre/post intervention studies that I am calculating Hedge's

I know how to calculate the difference of mean [= Mean(post)-Mean(pre)], but for the life of me cannot figure out how to calculate the difference of SD without having the individual scores.

Any ideas?

*g*for. All of the studies report the difference of mean and difference of standard deviation between pre/post for each group except one.I know how to calculate the difference of mean [= Mean(post)-Mean(pre)], but for the life of me cannot figure out how to calculate the difference of SD without having the individual scores.

Any ideas?

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