Chi-square test

fit<-gls(fcl~mass+activity+agility,correlation=corBrownian(phy=tree),data=df,method="ML",weights=varFixed(~vf))
Anova(fit)

De: "Fox, John" <jfox at mcmaster.ca>
Para: "Sergio Ferreira Cardoso" <sergio.ferreira-cardoso at umontpellier.fr>
Cc: "R-help list" <r-help at r-project.org>
Enviadas: S?bado, 21 De Janeiro de 2017 6:09:22
Assunto: Re: [R] Chi-square test

Dear Sergio,

You appear to have asked this question twice on r-help.

Anova() has no specific method for ?gls? models (I assume, though you don?t say
so, that the model is fit by gls() in the nlme package), but the default method
works and provides Wald chi-square tests for terms in the model. I don?t
understand the model formula x ~ 1 + 2 + 3 + x, however, and so I have no idea
what gls() would do with this model, other than report an error. Perhaps you
can show us the output ? or, better yet, provide a reproducible example.

As a general matter, for 1-df terms in an additive model, the 1-df chi-square
values reported by Anova() will simply be the squares of the corresponding Wald
statistics (labelled ?t? I believe) reported in the summary of the model.
Although the p-value is from the upper tail of the chi-square distribution, the
test is inherently two-sided.

Best,
John

-------------------------------------------------
John Fox, Professor
McMaster University
Hamilton, Ontario, Canada
Web: http::/socserv.mcmaster.ca/jfox

On Jan 20, 2017, at 8:36 AM, Sergio Ferreira Cardoso
<sergio.ferreira-cardoso at umontpellier.fr> wrote:

Dear all,

Anova() for .car package retrieves Chi-square statistics when I'm testing a
model the significance of a multivariate .gls model
gls(x~1+2+3+x,corBrownian(phy=tree), ...).
Is this Chi-square a two-sided test?

Thank you.

Best,
S?rgio.

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