I assume you are aware of the fact that the Student's t test assumes the means of the data to be normally distributed but does not require any normality assumptions concerning the data itself? If your data fulfills the requirements for the central limit theorem to hold (i.e. your observations are independently distributed) then I don't see any reason why you cannot use the simple t-test.

Zeno


-----Original Message-----
From: r-sig-finance-bounces@stat.math.ethz.ch on behalf of Reena Bansal
Sent: Wed 12/23/2009 4:33 PM
To: r-sig-finance@stat.math.ethz.ch
Subject: [R-SIG-Finance] Non parametric, unequal variance,equality of mean significance test
 
Hello everyone,

I have two samples of data of different sizes. Sample 1 is 30 points and
sample 2 is 20 points. I have no reason to believe that the two sample
are normally distributed or have the same variance. I am looking for
significance test for the null that the two samples have same mean (or
the two samples come from same population). 

I found the unpaired Student's t test for unequal variance. However this
test assumes normality.
The non parametric test I found is the Mann Whitney U test. But this
test requires equal variance.

Any suggestions.

Thanks,
Reena

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