Can you do a paired t test in SPSS or GraphPad with only means, errors and N? I have to verify some results. I have only the mean and its st. error, not the raw data. In a research paper they did a paired t test. Is it possible to check whether their p value is right by only using the means, st. errors and N, in SPSS or GraphPad?
 A: The first step in computing the paired t test is to compute the difference between each set of matched pairs (after - before in many cases). All the rest of the calculations are based on that list of differences. If you know the mean of the differences, as well as the SD (or SEM) and sample size, you can compute the paired t test. The t ratio equals the mean of the differences divided by the SEM of those differences. The df equals number of pairs minus 1. 
If you only know the mean and SD (or SEM) of the "before" data and separately the "after" data, then you cannot compute the paired t test. The information simply isn'there. 
A: In your situation - when you don't know anything about the within-pairs differences but know only statistics of the two matched samples separately - you need to know also the covariance or correlation between the two samples in order to be able to perform paired t-test.
Let's program paired t-test 'calculator' in SPSS matrix session, assuming that you know the covariance.
matrix.
*Enter the statistics: means, their errors, the covariance, and N.
compute MEAN1 = 1.6720.
compute SEM1 = .15315.
compute MEAN2 = 1.8674.
compute SEM2 = .14161.
compute COV = -.69211.
compute N = 50.

*Restore st. deviations out of st. errors.
compute S1 = SEM1*sqrt(N).
compute S2 = SEM2*sqrt(N).

*Paired t-test.
compute TVAL = (MEAN1-MEAN2)/sqrt((S1**2+S2**2-2*COV)/N).
compute PVAL = 2*(1-tcdf(abs(TVAL),N-1)).
print {MEAN1-MEAN2,TVAL,N-1,PVAL} /title 'Paired t-test result'
                  /clabels 'mean dif' 'stud t' 'df' 'p 2sided' /format f12.4.
end matrix.

***********
Paired t-test result
 mean dif       stud t           df     p 2sided
   -.1954       -.7323      49.0000        .4675

A: You are out of luck for the paired t test, since you don't have the necessary data, but for simple t tests based only on the summary statistics, the SPSSINC SUMMARY TTEST extension command allows you to do this from a dialog box.  You can get that command from the SPSS Community website at www.ibm.com/developerworks/spssdevcentral.  It requires the Python Essentials also available via that site, depending on your Statistics version.
