n <- c(1:10000)
plow <- pnorm(-0.2,mean=0,sd=sqrt(49/n))
pupp <- pnorm(0.2,mean=0,sd=sqrt(49/n))
p <- pupp - plow
plot(n,p,type="l",xlab="Dimensione del campione",ylab="Probabilità")
abline(h=0.95,lty=3,lwd=2)