Hello everybody,

I have some questions on ANOVA in general and on ANOVA in R particularly.
I am not Statistician, therefore I would be very appreciated if you answer
it in a simple way.

1. First of all, more general question. Standard anova() function for lm()
or aov() models in R implements Type I sum of squares (sequential), which
is not well suited for unbalanced ANOVA. Therefore it is better to use
Anova() function from car package, which was programmed by John Fox to use
Type II and Type III sum of squares. Did I get the point?

2. Now more specific question. Type II sum of squares is not well suited
for unbalanced ANOVA designs too (as stated in STATISTICA help), therefore
the general rule of thumb is to use Anova() function using Type II SS
only for balanced ANOVA and Anova() function using Type III SS for
unbalanced ANOVA? Is this correct interpretation?

3. I have found a post from John Fox in which he wrote that Type III SS
could be misleading in case someone use some contrasts. What is this about?
Could you please advice, when it is appropriate to use Type II and when
Type III SS? I do not use contrasts for comparisons, just general ANOVA
with subsequent Tukey post-hoc comparisons.

Thank you in advance,
Amasco

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