
ttest and normality
I keep reading that in order for a ttest to be valid the data need to be normal. I have distributions which are clearly skewed to the right (long right tails) so they are not normal. However I have a sample of of n>100 in both bases so the sampling distributions are essentially normal.
My question therefore is: does the ttest requirement for normality refer to the original distributions for the raw data, or for the sampling distributions for the sample means?
Thanks

Re: ttest and normality
The ttest itself, tests the sample mean, which will be normally distributed.
If your data itself is skewed but n is large enough the ttest is considered a robust test.
I would recommend using a ttest and then using a different test, maybe a nonparametric test like the KolmogorovSmirnov test.
Are the data sets considered different in both tests?