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Homework Help: Discrete Probability Mass Function

  1. Oct 18, 2011 #1
    1. The problem statement, all variables and given/known data
    A gas supply company is trying to set up contracts with two clients, A and B. The company will make a profit of ten million dollars for each contract that is successfully agreed. The probability of agreeing a deal with client A is 1/4 and the probability of agreeing a deal with client B is 1/2. The decisions of the two clients are independent. Let X be the total profit that the company will make from the two clients.

    a)Find the probability mass function of X

    b)Find the mean and variance of X



    3. The attempt at a solution

    I'm having a problem with setting up the PMF for this question.

    f_X(x) =
    1/4 for X = A
    1/2 for X = B

    This makes absolutely no sense. Furthermore, the sum of PMF has to equal to 1 but in this case, it isn't. I'm completely lost, how do I set up the PMF for this?
     
    Last edited: Oct 19, 2011
  2. jcsd
  3. Oct 18, 2011 #2

    LCKurtz

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    X is the total profit. You might start by listing the possible values X may take.
     
  4. Oct 19, 2011 #3
    Twenty million dollars, ten million dollars and zero dollars??

    (edit)nvm I figured out ty
     
    Last edited: Oct 19, 2011
  5. Oct 19, 2011 #4

    LCKurtz

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    I guess that means "never mind" and "thank you". You're welcome. Sometimes it just takes a little hint.
     
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