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Two fair dice are thrown, with the scores (X1, X2).

  1. Oct 12, 2011 #1
    Need help with this problem, please!

    Two standard, fair dice are thrown, and the scores (X1, X2) are recorded. Find the expected value of each of the following variables:
    (a) Y = X1 + X2
    (b) Z = X1*X2

    I don't even understand what it's asking! :( Any help is appreciated.
  2. jcsd
  3. Oct 13, 2011 #2


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    Science Advisor

    Expected value means average. For one die, it is 3.5. For the sum, the averages just add, so E(Y)=7. For the product you need to assume the dice are independent - in which case E(Z)=12.25 (the product).
  4. Oct 13, 2011 #3
    Not sure just providing the correct answer will be enough here. When you say you "don't even understand what it's asking" how much do you know? If I were to ask you the expected value of a single dice roll would you know how to arrive at the answer to such a question?
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