18. There are five numbers: 4, 7, 1 1, 13, 15, I pick one at random (with equal probability). I repeat this until I have done this for 100 times. I then calculate the mean of these 100 numbers. If 1 then repeat this entire process over and over - ten thousand times - until 1 have a list of ten thousand means, What is the approximate standard deviation of these means? become nomal standard