d = read.table("exmp11-01.txt",header=TRUE,sep=",")
d$box = as.factor(d$box)
fit = aov(strength~box,data=d)
summary(fit)
qqnorm(fit$res);qqline(fit$res)
install.packages("car")
library(car)
fit2 = leveneTest(d$strength,d$box,center=mean)
print(fit2)
TukeyHSD(fit)
plot(TukeyHSD(fit))
abline(v=0)