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##R tutorial 02

my.url<-'http://www.math.mcgill.ca//dstephens//204//Data//GOLFCRD.dat'

Golf <- read.table(url(my.url),header=FALSE)

names(Golf)<-c("Brand","Distance")

str(Golf)

?str

summary(Golf$Distance)

tapply(Golf$Distance,Golf$Brand,mean)
tapply(Golf$Distance,Golf$Brand,var)

tapply(Golf$Distance,Golf$Brand,summary)

boxplot(Distance~Brand,data=Golf,col="red")

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summary(aov(Distance~Brand,data=Golf))

k<-4
n<-nrow(Golf)

#compute the critical value
(CR<-qf(0.95,k-1,n-k))

xv<-seq(0,5,by=0.01)
yv<-df(xv,k-1,n-k)

plot(xv,yv,type="l")
title("Fisher-F(3,36) density")

abline(v=CR,col="red")