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Homework Help: Central Limit Theorem Question

  1. Nov 28, 2009 #1
    1. The problem statement, all variables and given/known data
    On average one third of seniors at a college will be bring parents to the graduation, one third will bring one parent and the remaining third will not bring any parents. Suppose there are 600 seniors graduating this year. Estimate the probability that more than 650 parents will attend the graduation.

    2. Relevant equations
    The Central Limit Theorem

    3. The attempt at a solution
    I let X = the number of parents in attendance and Xi = the number of parents brought by student i. So X = X1+...+X600.
    I found that E(X)=600 and in order to use the Central Limit Theorem I need to know the variance of X, but this is what is tripping me up.
    Var(X) = E(X2) - (E(X))2 but I don't know how to find (E(X))2. Is there an entirely different approach that I'm missing?
  2. jcsd
  3. Nov 28, 2009 #2
    Okay, never mind I think I got it...
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