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Math Help - Basic Statistics. Help please

  1. #1
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    Question Basic Statistics. Help please

    Hi, I would appreciate any guidance to do this exercise. I'm a lawyer and I'm quite lost with the subject:

    Te question is:

    Consider the following probability distribution:

    X P(X)

    -1 0.17
    2 0.15
    5 0.40
    8 0.18
    11 0.10
    1.00

    They ask (answer to four decimal places):

    E(X)= _ _. _ _ _ _
    V(X)= _ _. _ _ _ _


    Your help is much appreciated.

    Mauricio
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  2. #2
    Newbie JohnM's Avatar
    Joined
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    Quote Originally Posted by 10219929 View Post
    Hi, I would appreciate any guidance to do this exercise. I'm a lawyer and I'm quite lost with the subject:

    Te question is:

    Consider the following probability distribution:

    X P(X)

    -1 0.17
    2 0.15
    5 0.40
    8 0.18
    11 0.10
    1.00

    They ask (answer to four decimal places):

    E(X)= _ _. _ _ _ _
    V(X)= _ _. _ _ _ _


    Your help is much appreciated.

    Mauricio
    E(X) = expected value = summation of X*P(X) --> same as a weighted average

    V(X) = variance = summation of [ X - E(X) ]^2 * P(X)
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  3. #3
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    Sep 2006
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    Thanks John

    For V(X), that means that I have to use the sumation of all X values, plus the result of the sumation of E(X)? Sorry mate, can you give just one example using the numbers? Thanks a lot. Mauricio
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  4. #4
    Newbie JohnM's Avatar
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    Quote Originally Posted by 10219929 View Post
    For V(X), that means that I have to use the sumation of all X values, plus the result of the sumation of E(X)? Sorry mate, can you give just one example using the numbers? Thanks a lot. Mauricio
    Yes, for V(X) you will use the result from computing E(X).

    Here's an example:
    Expectation
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