Dear all,
I use a nested design with lm and glm, with factor2 nested within
factor1. In order to test for the significance of both factors, I use
anova tables on the obtained models such as follows:
/> mod1<-lm(A~factor1/factor2)
> amod1<-anova(mod1, test="F")
Analysis of Variance Table
Response: A
Df Sum Sq Mean Sq F value Pr(>F)
factor1 15 85.99 5.73 3.1332 8.702e-05 ***
factor1:factor2 42 131.75 3.14 1.7145 0.005654 **
Residuals 308 563.52 1.83 /
and recalculate the Fvalue for factor1 as follows:
/> ffactor1<-(85.99/15)/(131.75/42)
> fpop
[1] 1.827491
> 1-pf(ffactor1,15,42)
[1] 0.06285258/
My question is: am I allowed to do the same with an Analysis of Deviance
table, calculated on a glm model, as done hereafter:
/> mod2<-glm(M~factor1/factor2, family=Gamma(link=identity))
> amod2<-anova(mod2,test="F")
> amod2
Analysis of Deviance Table
Model: Gamma, link: identity
Response: M
Terms added sequentially (first to last)
Df Deviance Resid. Df Resid. Dev F Pr(>F)
NULL 365 164.486
factor1 15 18.699 350 145.787 3.4365 1.997e-05 ***
factor1:factor2 42 38.973 308 106.814 2.5579 2.319e-06 ***
---
> ffactor1<-(18.699/15)/(38.973/42)
[1] 1.343422
> 1-pf(ffactor1,15,42)/
[1] 0.2206373
Thanks in advance for your answer, and sorry if my question doesn't fit
with the R-help list.
Agn?s Coutellec
--
Marie-Agn?s Coutellec
UMR INRA-Agrocampus 985 EQHC
Equipe Ecotoxicologie et Qualit? des Milieux Aquatiques
65 rue de Saint-Brieuc - CS 84215
35042 Rennes cedex - FRANCE
t?l.: +33(0)2 23 48 52 48
fax: +33(0)2 23 48 54 40
