I need to run a t-test on a two sample group that is unpaired with unequal variance for a specific mean difference.

The data sample is unpaired and my research hypothesis is:
Upstream- Downstream “at least” (one sided) ≥ 0.5ppm
I found a note that STATA cannot do this:
Unlike the SAS TTEST procedure, the .ttest command cannot specify the mean difference D0 other than zero.
http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf

If the data were paired I could create a new variable with the difference and run a ttest on that for the specified ppm.



The "R" code is:
t.test(Upstream,Downstream,alternative="greater",m u=0.5,conf.level=0.99)

Thanks,

Just a Noobie, Matt