|CC:||erich.greene [...] yale.edu|
|Subject:||Mixed ANOVA with 3-level between-subjects variable -- uninvertible matrix|
From Erich Greene: Following up on the within factor masquerading as a between, I took a look at the original mixed model test (t_anova_rptd_mixed) and found the problem there as well: $a and $b are both within-subject factors. So working with the intended 3-level within * 2-level between model from that test (changing the original subject vector from 0..3x6 to 0..7x3 makes $b between-subjects), I again found a dependence on the order of the data within the piddles. (In principle, we should get the same results no matter how we permute the input vectors, as long as we apply the same permutation to all of them.) While it runs with both orderings, the output is only correct when the data is grouped by subject (my frontends all do this, which is why I'd never noticed a problem before); when the data is grouped by within var level, the error sums of squares are wrong (though the degrees of freedom are correct, unlike in the 3-level between case).