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Discrete probability distributions

  1. Aug 1, 2014 #1
    1. The problem statement, all variables and given/known data
    Here's the question:
    Given X is a discrete random variable. E(X-2) = 1/3 , VAR(X-2) = 20/9 .
    Detrmine value of E(X^2)
    the ans is 23/3 . but i ended up getting 3 . why i am wrong?


    2. Relevant equations



    3. The attempt at a solution
     

    Attached Files:

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  3. Aug 1, 2014 #2

    Ray Vickson

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    ##\text{Var}(X-2) = \text{Var}(X)## because ##\text{Var}(\cdot)## is unaffected by a non-random shift. Also: ##\text{Var}(X) = E(X^2) - (EX)^2##.
     
  4. Aug 2, 2014 #3

    ehild

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  5. Aug 2, 2014 #4

    Ray Vickson

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