Quick reaction, Rick:
For the "statistically challenged" I'd be tempted to try the following;
maybe there are reasons you know of in the situation that would make it
... umm ... impolitic.
Anyway: It looks as though no one is interested in pursuing
interactions among the several categorical Xj's, not among the continuous
predictors, nor between the two sets. (Now, _I_ would be interested in
pursuing such things, but that's another story.)
On that assumption, one could do a one-way ANOVA of Z on the
category system X1; take the residuals from that and enter them into a
onew-ay ANOVA on X2; etc. The residuals from the final categorical
predictor can then be regressed on the several continuous predictors.
From one point of view, one might have preferred to do a k-way
analysis of covariance with (is it only 2?) covariates, and avoid the
messiness of stagewise procedures; but I'd bet the implied design is not
only not balanced but nowhere NEAR being balanced. It can be argued that
what I've suggested is kind of approximate, but I think it will show
whether there's anything interesting there that one might want to pursue
more intensively.
Time for class, gotta run. Just a thought, I haven't reflected
deeply on it.
Best regards!
-- Don.
------------------------------------------------------------------------
Donald F. Burrill [EMAIL PROTECTED]
348 Hyde Hall, Plymouth State College, [EMAIL PROTECTED]
MSC #29, Plymouth, NH 03264 603-535-2597
184 Nashua Road, Bedford, NH 03110 603-471-7128
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