From: Martin Julien <martin.julien.2_at_courrier.uqam.ca>

Date: Wed 18 Jan 2006 - 07:33:57 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Jan 18 07:59:19 2006

Date: Wed 18 Jan 2006 - 07:33:57 EST

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.

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 ?

In R

> anova (lm(Y~X.1+X.2))

Analysis of Variance Table

Response: Y

Df Sum Sq Mean Sq F value Pr(>F) X.1 1 4.0351 4.0351 6.5187 0.01852 X.2 1 0.5903 0.5903 0.9537 0.33991 Residuals 21 12.9991 0.619

> anova (lm(Y~X.2+X.1))

Analysis of Variance Table

Response: Y

Df Sum Sq Mean Sq F value Pr(>F) X.2 1 1.9651 1.9651 3.1747 0.08926 X.1 1 2.6603 2.6603 4.2977 0.05066 Residuals 21 12.9991 0.619

With another stat software (JMP)

Y~X.1+X.2

Df Sum Sq Mean Sq F value Pr(>F) X.1 1 2.6603 2.6603 4.2977 0.05066 X.2 1 0.5903 0.5903 0.9537 0.33991 Residuals 21 12.9991 0.619 Y~X.2+X.1 Df Sum Sq Mean Sq F value Pr(>F) X.2 1 0.5903 0.5903 0.9537 0.33991 X.1 1 2.6603 2.6603 4.2977 0.05066 Residuals 21 12.9991 0.619 ---------------------------------------------------------------------------Julien Martin

Canadian Research Chair in behavioural ecology Université du Québec à Montréal

Email: martin.julien.2@courrier.uqam.ca

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Jan 18 07:59:19 2006

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