You have all the information that you need to do the pooled t-test using
the formula in many intro stats textbooks and probably on wikipedia as
well, just plug your numbers into the formulas in the book (R can act as
the calculator to make this easier).

Or sometimes simpler (for the human, the computer does more work, but that
is what it is for) is to do like chuck.01 suggests and simulate the data,
however chuck.01 left out a step, you should make sure that the simulated
data has the exact same mean and standard deviation as you provide, then
the results will be the same as if you used the formula (other than
possible slight rounding errors).  Generate the 2 samples from normals with
mean 0 and standard deviation 1, then use the scale function to make sure
that the means are exactly 0 and standard deviations exactly 1.  Now
multiply by the proper standard deviation then add the appropriate mean,
then use the t.test function to analyze.


On Sat, Nov 24, 2012 at 11:28 AM, Lorenzo Isella
<lorenzo.isella@gmail.com>wrote:

> Dear All,
> A problem almost taken from a textbook: I have two independent samples
> (which are both assumed to come from a normal distribution).
> The sample sizes are N1 and N2, the sample means are x1 and x2 and the
> sample standard deviations are s1 and s2 (the standard deviations are
> close).
> I would like to conduct a two sample t-test with equal variances at
> alpha=0.05 (and then remove the assumption of equal variances).
> I have come across several resources
>
> http://bit.ly/WKGuHV
> http://bit.ly/WKGwzG
>
> but the difference here is that I have access only to the N,x and s for
> the two samples, NOT to the results of every observation (i.e I know for
> instance N1 x1 and s1, but I do not have the corresponding list of N1
> values).
> Many thanks for any suggestions.
> Best Regards
>
> Lorenzo
>
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>



-- 
Gregory (Greg) L. Snow Ph.D.
538280@gmail.com

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