I had to compare whether the two groups is somehow of the same distribution the problem is I only have 3 samples from each group in millimeters, say, Group A is 29mm, 32mm and 31mm while the other group is 35 mm in all three samples. What statistical treatment should I use? Im thinking mann whitney but not so sure... t test is possible but im not sure with the underlying assumptions... please help me with this.
With two groups of 3, significant differences in the mean or variance will have to pass the interocular trauma test - IOTT - it hits you between the eyes. Certainly you can do a test of the means (@Glen_b suggests Welch t-test, and that's a good suggestion) but how do you hope to find something significant,, regardless of whether you assume equal variances or not?
So I would say the best you can do is to present the 6 values and let people think about it for themselves.