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Math Help - Another probability one

  1. #1
    Junior Member
    Joined
    Jun 2008
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    53

    Another probability one

    Let the random cariable X be the number of days that a patient needs to be in the hospital. X has the pmf

    f(x) = (5-x) / 10 x=1, 2, 3, 4

    The patient receives $200 for day one and two, and $100 for days 3 and 4, what's the expected payment to the hospital?
    ---

    I thought that, expected value is the sum of the probability of a certain outcome times the amount to pay for each outcome. So

    E(f) = f(1)*200 + f(2)*200 + f(3)*100 + f(4)*100
    = 2/5*200 + 3/10*200 + 1/5*100 + 1/10*100
    = 80 + 60 + 20 + 10
    = $170


    But my book has $360 for the answer =/
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  2. #2
    Super Member malaygoel's Avatar
    Joined
    May 2006
    From
    India
    Posts
    648
    Hi!

    Payment after 1st day =$200
    Payment after 2nd day= $200+$200=$400
    Payment after 3rd day=$200+$200+$100=$700
    Payment after 4th day=$200+$200+$100+$100=$800

    Rest working is correct.


    Malay
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