Hi,

I have tried to solve this problem for a quite long time. I hope that you can help me out. :)

My data set is like this:

Within factor: time (pre- and post-test results)
Between factor: treatment (3-level)

I have run the repeated measure ANOVA. The results of the Muachly's test of sphericity has no number under the significance column. The df value is 0.

These were the results I got:

Mauchly's W = 1.000
Approx. Chi-Square = .000
df = 0
Sig. = .


I read from somewhere that the repeated measures ANOVA should not have been done with this kind of set. It said that sphericity is meaningful only when the within-subject factor has more than two levels.

I don't quite understand this. Originally I did run ANCOVA using the pre-test as a covariate. But my professor recommended me to do the repeated measures ANOVA. I need to know the rationale behind of choosing ANCOVA over the repeated measures anova.

Could you please explain this or let me know where I can find more information on this?

Thank you.
.