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st: MANOVA


From   David Airey <david.airey@vanderbilt.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: MANOVA
Date   Wed, 27 Aug 2003 15:27:30 -0500

"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)?

-Dave

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