Sphericity

Pierre

Hello,
In Assumption checks for the test of sphericity with AnovaRM with two levels, an annotation indicates "When the repeated measure has only two levels, the assumption of sphéricity is always met". Have you any references, please?

Thanks in advance.

Regards.

cesco

The assumption of sphericity is met when the variances of the differences are equal. With two levels, you only have one difference (level 1 - level 2) with nothing left to compare this difference with. Hence thusly, your data is inherently spherical.

EJ

Thanks for responding, Cesco -- I somehow missed this question

Pierre

Thanks for this very clear answer.