Hello,
With regard to Mauchly's test of Sphericity in order to assess
validity of F statistic calculated for a one way repeated measures
anova:
I understand why Mauchly's test of Sphericity has no meaning when
there are are only 2 levels of a repeated measures factor.
However, I notice (using GLM.....repeated measures in SPSS) that
Mauchly's test of Sphericity also appears to be undefined (or gives
the useless output of Mauchly's W = '.0' , p = '.') when the number of
levels of a repeated measure is equal to or greater than the number of
cases (subjects). In these instances, even though Mauchly's statistic
is not calculated, Greenhouse-Geisser, Huynh-Feldt, and Lower-Bound
Epsilon values are calculated.
I would be really happy if someone could provide some insight on why
Mauchly's statistic is not calculated in these cases and what should
be done to assess sphericity in the absence of Mauchly's statistic.
I have noticed the question asked previously on other forums but have
never seen a response.
Thank you
Omar
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