gpa=read.table("D:gpa.txt",header=T)
attach(gpa)
hist(GPA)
boxplot(GPA)
qqnorm(GPA)
qqline(GPA)
sampling=function(a,N,n){
mu.a=mean(a)
sd.a=sd(a)
x.bar=rep(NA, N)
for (i in 1:N) { 
  x.bar[i]=mean(sample(a, n, 
replace=TRUE))
   }
hist(x.bar, freq=FALSE, 
main=paste("Sampling Distribution, N="N,
"n=",n))
}
a=sampling(sample(GPA),N=1000,n=10)
x=GPA[major==0]
y=GPA[major==1]
var.test(x,y)
t.test(x,y,var.equal=TRUE)