I have a 3 (within) X 2 (between) design. For the within-subject aspect, is it possible to statistically compare the amount of variability in one session with the amount of variability in another session for a given group. I understand the concept of sphericity with more than 2 repeated levels, however I am not necessarily interested in the variation in difference scores from my three levels, or am I? (My repeated measures are spherical, but have accounted for this in my analyses). So, my question would be, is a test of sphericity the same as testing the differences in variance between repeated sessions, regardless of the number of levels? Further, I am conceptualizing the test that I desire as similar to a two group between subjects test of homogeneity, only that it would be used to look at change in variability from 2 of my repeated levels (2 and 3). Sphericity takes into account my level 1, correct; and is impossible in a two level test, correct? I will conceed and am afraid that I may be attempting to butcher some assumption I am unaware of, or may have even overlooked somthing simple, so please be kind I thought about rearranging the data so that my within levels can be tested with a between subjects test of homogeneity (like levene's), sounds ugly though so I never did this. If this makes sense and can be done, hints toward what test would be appropriate would be great. I regard to the earlier threads, I have spent too many hours thinking about this and I have finally conceeded to ask, so I have done my homework. Thanks a lot in advance for your time.