"Cases when the MANOVA approach cannot be used. There are instances
(designs) when the MANOVA approach cannot be applied; specifically,
when there are few subjects in the design and many levels on the
repeated measures factor, there may not be enough degrees of freedom to
perform the multivariate analysis. For example, if we have 12 subjects
and p = 4 repeated measures factors, each at k = 3 levels, then the
four-way interaction would "consume" (k-1)p = 24 = 16 degrees of
freedom. However, we have only 12 subjects, so in this instance the
multivariate test cannot be performed."
In my case, I was considering, 4 repeated measures factors, with levels
4, 3, 2, and 2, in which the four way interaction would consume 4*3*2*2
= 48 df. In my case I will have 400 subjects total, with between
subject factors sex and strain, with 10 per sex*strain combination.
Does the interaction df limit refer to the total subjects (400), or the
subjects in a between factor group (10)?