Joseph Coveney kindly notes:
A couple of quick observations: (1) David might have trouble with
-manova-
since each mouse has 48 observations worth of covariances to estimate
and only
eight records (animals) to do it with (and even with the full dataset
of 20
strains and 38,400 observations--or 800 animals--it would still appear
problematic to estimate the 1100-1200 elements in the
variance-covariance
matrix),
This is good to know. I discussed the design with a couple scientists
who didn't suggest my intended data set would be shy in terms of the
number of animals for the effects I want estimated. I'll ask again with
these points your have raised. Fortunately, my study is in the
beginning of data collection, and I while it is too expensive with my
resources to obtain more within strain data in terms of animals, I
could simplify the design by dropping one within subject effect which
is not obligatory, and I could treat another as a single variable time
effect, leaving two within-subject factors.
(2) this might be why the -repeated()- option is having trouble, too,
since it's trying to estimate deviation from sphericity/compound
symmetry in
the same vein, (3) the ANOVA table was completed and, if David assumes
sphericity (which he might have to do, given the number records/mice to
actually assess the assumption), then the analysis has completed as
far it can--
and this might be true with any software package that estimates
epsilons. (I
believe that SAS's PROC MIXED is able to partition the
variance-covariance
matrix into blocks according to the within-subject factor so that
fewer off-
diagnonal elements need to be estimated, and this might enable
full-rank MANOVA
to be done here.)
This is also very good to know. If SAS rips through these examples with
SAS MIXED but stumbles with GLM, that will be a good hint your are
right.
Other than a typographical error in mine (a missing forward slash in
one line
of the model specification), our models are fundamentally the same:
both
David's and mine are repeated-measures (split-plot) analyses of
variance; I
didn't include the -repeated()- option in my repeated-measures ANOVA
because I
had only two levels for each within-subject factor, rendering the
option
unnecessary.
I forgot that; it was even pointed out to me in another context by Ken
Higbee a while back. Thank you so much for taking an interest on this.
I'll see if my computer handles your do file in 30 minutes.
I've never tried it, so I'm not sure whether a zero residual mean
square will affect the -repeated()- option's operation.
I'll check this too with your do file.
P.S. The post appears in monotype font in my browser.
Ah ha! It's a bug in Safari 1.0 then.
Thank you again.
-Dave
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