Thorn,

All the formulas you listed make sense.  Remember that the notation x:y is
an indexing scheme
for dummy variables.  It is not a statement about degrees of freedom.  The
dummy variables
specified may be linearly dependent on earlier dummy variables in the system

x/y is correctly expanded to x + x:y and in an anova setting has
a-1 and a(b-1) degrees of freedom.

x*y is correctly expanded to x + y + x:y and in an anova setting has
a-1,  b-1, and (a-1)(b-1) degrees of freedom.
Rich

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