# R. Chris Fraley | Nov 29 2002
# Estimate statistical power of a correlation
 
# To use this program, simply plug in the expected or hypothesized correlation
# and the corresponding sample size.
# At the end, the program will tell you the proportion of times that you'll obtain
# a p-value less than 5%.

n<-160
r<-.22

#-----------------------------------------------------------
# The rest of this doesn't need to be adjusted by the user.
#-----------------------------------------------------------

trials<-1000

p.vec<-rep(99999,trials)
for(i in 1:trials){
	x1<-rnorm(n)
	x2<-r*x1 + rnorm(n,0,sqrt(1-r^2))
	p.vec[i]<-cor.test(x1,x2)$p.value

}

cat("Proportion of times the null hypothesis will be rejected ","\n") 
print(table(p.vec<=.05)/trials)