1. The problem statement, all variables and given/known data Let X1,X2,...X10 be independent normal random variables with mean 10 and std dev 4. Let Y = X1+X2+...+X10. Let X be Y/10. What is P(X < 8) 2. Relevant equations E(X) = 10 and Var(X) = 42 / 10 = 1.6 std dev of X = 1.6.5 = 1.26 3. The attempt at a solution To convert to standard normal distribution to use z table to solve I get.. P(X-10/1.26 < (8-10)/1.26) = P(Z < -1.58) = 0 I really doubt that I have done this problem correctly because it is on a sample exam and seems too easy. Have I done anything incorrectly or am I just second guessing myself needlessly?