Re: [R] Anova problem with order of terms in model

From: Berton Gunter <>
Date: Wed 18 Jan 2006 - 08:13:34 EST

I suggest you consult a local statistician or read up on linear models,perhaps by reading the relevant section of V&R's MASS. Also search the R-Help archives for "Type III SS." Further comments below.

"The business of the statistician is to catalyze the scientific learning process." - George E. P. Box    

> -----Original Message-----
> From:
> [] On Behalf Of Martin Julien
> Sent: Tuesday, January 17, 2006 12:34 PM
> To:
> Subject: [R] Anova problem with order of terms in model
> Hi
> I have a linear model and I want to tests whether the model terms are
> significant
> I used anova but F and P value depend on the order of the terms in the
> model.

Correct. Differennt hypotheses are being tested. R does **sequential** SS (this preserves additivity/orthogonality of contrasts being tested). In a non-orthogonal designs, these depend on order.

> I have repeated the same analysis in another stat software
> and F and P value
> did not differ with order of terms in the model.
> Can anyone can explain what happen or what am I doing wrong ?

And this "other software" is not doing a sequential SS, but rather what is usually called Type III SS (google on "Type III SS" for more info). mailing list PLEASE do read the posting guide! Received on Wed Jan 18 08:31:02 2006

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