Expert: Asmaa Abd Elhameed Ahmed - 10/4/2009

Question
Hi, when using the mann-whitney ranking test, can I use it on both untransformed and log transformed data? There wouldnt be any difference right because rankings dont change?

thanks


Answer
hi,
Mann-Whitney test used to compare quantitative not normally distributed data  between 2 groups
or when sample size is small.
It can be used for both untransformed and untransformed data,but you already transform the data to apply parametric tests(at-test) ,so, if still not normally distributed after transformation it is better to apply Mann-Whitney on the untransformed