R help - Oct 2003 - Type III Sum of Squares Calculation

HI All:

Can anyone give me the formulae/steps for calculating the type III sum of
squares for an unbalanced 2-way ANOVA design?  Eg. we are looking at 8
treatments x 4 doses, with unequal numbers of replications within the
groups.  I really need the stepwise calculation, as I would try to put it
in my own code (possibly in Visual Basic) to automate the task.

Thanks very much.

Karth.

Dear Karth,

The Anova function in the car package can calculate "type-III" sums of
squares, though it doesn't do so by default. Be careful with the contrast 
coding or you will get nonsense (and you might want to think about whether 
you really want type-III SSs).

I hope that this helps,
  John

At 08:01 AM 10/21/2003 -0400, Subramanian Karthikeyan
wrote:
>HI All:
>
>Can anyone give me the formulae/steps for calculating the type III sum of
>squares for an unbalanced 2-way ANOVA design?  Eg. we are looking at 8
>treatments x 4 doses, with unequal numbers of replications within the
>groups.  I really need the stepwise calculation, as I would try to put it
>in my own code (possibly in Visual Basic) to automate the task.
-----------------------------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox at mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox