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Homework Help: Normal Random Variables Question

  1. May 29, 2010 #1
    1. The problem statement, all variables and given/known data

    Problem 1 – Normal Random Variables

    B) Y ~ N(300, 100). Pr (300 < Y < 320) = 0.4772

    D) H ~ N(4000, 25). R = f(H) = 0.5H – 60. E(R) = 1940; Var(R) = 156.25

    I have a problem solving these problems above...I missed the class when we covered this subject and now I am lost upon solving them.. I hope somebody can help, thanks a lot
  2. jcsd
  3. May 30, 2010 #2


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    Homework Helper

    For a normally distributed random variable,

    P(a < X < b) = P(X < b) - P(X < a)

    For any random variable [itex] W [/itex], if [itex] a, b [/itex] are real numbers,

    Z = aW + b


    E(Z) = aE(W) + b, \quad Var(Z) = a^2 Var(W)

    (as long as the mean and variance of [itex] W [/itex] exist)
  4. May 31, 2010 #3
    Thanks for the reply!!

    However, when I plug it in I dnt get the right answer.... did u check if the given answer is right?
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