# Re: [R] different F test in drop1 and anova

From: Tom Van Dooren <vdooren_at_rulsfb.leidenuniv.nl>
Date: Fri 21 Oct 2005 - 04:33:47 EST

Hi Brian,
well I wanted a test based on quasibinomial... Does it work like this then?:

x<-gl(3,2)
y<-c(0,1,0,0,1,1)

# quasibinomial models #

```########################

```

qb1<-glm(y~x,quasibinomial)
qb2<-glm(y~1,quasibinomial)

qbdev<-(qb2\$dev-qb1\$dev)

qbdev # deviance I

qbdev/(qb2\$df.res-qb1\$df.res)/(qb1\$dev /qb1\$df.res) # deviance ratio II

qbdev/summary(qb1)\$disp # scaled deviance III

qbdev/(qb2\$df.res-qb1\$df.res)/summary(qb1)\$disp # scaled deviance IV

```anova(qb2,qb1,test="Chisq") # Chisq test based on I
drop1(qb1,test="F") # F test, based on II
drop1(qb1,test="Chisq") # Chisq test, based on III
anova(qb2,qb1,test="F") # F test, based on IV

```

# binomial models #

```###################

```

b1<-glm(y~x,binomial)
b2<-glm(y~1,binomial)

bdev<-(b2\$dev-b1\$dev)

bdev # deviance I

bdev/(b2\$df.res-b1\$df.res)/(b1\$dev /b1\$df.res) # deviance ratio II

```drop1(b1,test="Chisq") # Chisq test, based on I
anova(b2,b1,test="Chisq") # Chisq test based on I
anova(b2,b1,test="F") # Chisq test, based on I
drop1(b1,test="F") # F test, based on II

```

Cheers, Tom

PS: thanks Tord ;)

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