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The NESTED Procedure |
A completely
nested design is defined to be unbalanced if the groups
corresponding to the levels of some classification variable
are not all of the same size. The NESTED procedure can
compute unbiased estimates for the variance components in an
unbalanced design, but because the sums of squares on which
these estimates are based no longer have
distributions under a
Gaussian model for the data, F tests for the significance
of the variance components cannot be computed. PROC NESTED
checks to see that the design is balanced. If it is not, a
warning to that effect is placed on the log, and the columns
corresponding to the F tests in the analysis of variance
are left blank.
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