[R] Denominator Degrees of Freedom in lme() -- Adjusting and Understanding Them

[Douglas Bates]

Contributions of code to provide alternative calculations of
denominator degrees of freedom are welcome :-)

I think it would be good to bear in mind that the use of the t and F
distributions for models with mixed effects is already an
approximation.  If your design is such that you end up with a very few
denominator degrees of freedom then the whole question of whether you
should be using F or t distributions in the first place becomes
problematic.   If the number of denominator degrees of freedom is
moderate than the distinction between alternative methods becomes
unimportant.

-- 
Douglas Bates                            bates at stat.wisc.edu
Statistics Department                    608/262-2598
University of Wisconsin - Madison        http://www.stat.wisc.edu/~bates/