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I have a study which provides the mean difference for two groups (alongside 95%CI, SE, n and p-value). I would like to extrapolate the raw means to use in Revman to perform a random-effect SMD meta-analysis. Can I extrapolate the raw means from the MD?

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  • $\begingroup$ Do you have either of the group means? $\endgroup$ – gung - Reinstate Monica May 2 '16 at 14:27
  • $\begingroup$ Nope, paper doesn't give them sadly $\endgroup$ – samleighton87 May 2 '16 at 14:48
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This is tantamount to asking whether, if you knew $x + y = 20$, can you identify $x$ and $y$ uniquely. The answer is, of course, no. There are infinitely many possible solutions.

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If RevMan is computing the mean difference internally then it may be that you can supply any two means which have the required mean difference. Try it and see. More specifically if the mean difference you have is 10 then run it with 0 and 10 and then again with 990 and 1000. If RevMan gives you the same answer then you are in clover.

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  • $\begingroup$ So you are pretty much right - I don't need raw means I can just do a Generic Inverse Variance Meta-Analysis using the mean differences and standard error! $\endgroup$ – samleighton87 May 2 '16 at 16:05
  • $\begingroup$ I do not use RevMan myself so I was not sure whether that would work for you. $\endgroup$ – mdewey May 2 '16 at 16:09

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