1. The problem statement, all variables and given/known data In a random number game, the lottery, I need to know the probability of a number being drawn over a number of draws. Each ball of has a chance of 1 in 7 of being drawn in a draw. If the expected frequency of each ball is 200 (over 1400 draws) I need to know how to work out the probability of a ball being drawn 170 or 230 times rather than the expected 200. 3. The attempt at a solution All I can think of is using the normal distribution but I can't see how to use it here. I have no s.d. also this is a discrete random variable.