#  one way ANOVA
tire<-read.csv("c:/RData/tire.csv", header=T)
tire
attach(tire)
str(tire)
detach(tire)

tire1<-read.csv("c:/RData/tire_1.csv", header=T)
tire1
str(tire1)
tire1$brand1<-as.factor(tire1$brand1)
str(tire1)

tire<-read.csv("c:/RData/tire.csv", header=T)
tire
attach(tire)
table(brand)
tapply(life, brand, summary)
tapply(life, brand, sd)
boxplot(life~brand, main="tire life by brand",
        yaxt="n", xlab="brand", ylab="life", col=terrain.colors(4))
fit <- aov(life ~ brand, data=tire)
fit
anova(fit)
model <- lm(life ~ brand, data=tire)
model
anova(model)

# Fisher LSD
install.packages("agricolae")
library(agricolae)
fit<-aov(life ~ brand, data=tire)
out <- LSD.test(fit,"brand", p.adj="none")
out
LSD <- qt(1-0.025, 40-4)*sqrt(30.84617*(1/10+1/10))
LSD

# Scheffe
comparison <- scheffe.test(fit,"brand", group=TRUE, console=TRUE,
    main="Life of tire with different brand")
comparison
diff <- sqrt((4-1)*qf(1-0.05, 4-1, 40-4)*30.84617*(1/10+1/10))
diff