cnt = 0
for (i in 1:500) {
  x = rnorm(500,0,1)
  y = t.test(x,conf.level = 0.9)
  if(y$conf.int[1] <= 0) {
    if(y$conf.int[2] >= 0){
      cnt = cnt + 1
    }
  }
}
cnt/500.0