[R] Type II and III sum of square in Anova (R, car package)

[Bill.Venables at csiro.au]

I cannot resist a very brief entry into this old and seemingly
immortal issue, but I will be very brief, I promise!

Amasco Miralisus suggests:

> As I understood form R FAQ, there is disagreement among Statisticians
> which SS to use
>
(http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-does-the-output-from-a
nova_0028_0029-depend-on-the-order-of-factors-in-the-model_003f).

To let this go is to concede way too much.  The 'disagreement' is
really over whether this is a sensible question to ask in the first
place.  One side of the debate suggests that the real question is what
hypotheses does it make sense to test and within what outer
hypotheses.  Settle that question and no issue on "types" of sums of
squares arises.

This is often a hard question to get your head around, and the
attraction of offering a variety of 'types of sums of squares' holds
out the false hope that perhaps you don't need to do so.  The bad
news is that for good science and good decision making, you do.

Bill Venables.