Dear Martin, The anova() function computes sequential (sometimes called "type-I") tests; I'm not sure what Jmp does by default, but either "type-II" or "type-III" tests would produce these results for a model of this structure. See the Anova() function in the car package for "type-II" and "III" tests.
I hope this helps, John -------------------------------- John Fox Department of Sociology McMaster University Hamilton, Ontario Canada L8S 4M4 905-525-9140x23604 http://socserv.mcmaster.ca/jfox -------------------------------- > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Martin Julien > Sent: Tuesday, January 17, 2006 3:34 PM > To: r-help@stat.math.ethz.ch > 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. > 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: [EMAIL PROTECTED] > > ______________________________________________ > 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 ______________________________________________ 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
