Hi John,
I think you should have a look at pooled standard errors which you can use to estimate the combined standard error for the two samples.
Example below: 
SEx1-x2 = sqrt [ s21 / n + s22 / m ] 
Hope this helps.
Cheers 
 
Kind regards

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On Monday, December 29, 2014 11:12 AM, John Sorkin <[log in to unmask]> wrote:


How can I compute the SE (standard error) of the concatenation of two samples?
Assume sample 1 has n observations,
            sample 2 has m observations
The concatenation of sample 1 with sample 2 would have n+m observations.
If I know the mean of sample 1 = m1, and SE sample 1=se1, 
              the mean of sample 2 = m2, and SE sample 2=se2,

can I use n, m1, se1, m, m2, se2 to compute the SE?

Thank you,
John





John David Sorkin M.D., Ph.D.
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