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Math Help - finding the standard deviation of a radom variable??

  1. #1
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    finding the standard deviation of a radom variable??

    can anybody solve this.
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  2. #2
    Moo
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    Quote Originally Posted by arslan View Post
    can anybody solve this.
    Compute \mathbb{E}(X)=\sum_{i=1}^3 x_i \mathbb{P}(X=x_i)=0.2 \times 10+0.3\times 20+0.5\times 30

    Complete the table with the values of x^2
    Then compute \mathbb{E}(X^2)=\sum_{i=1}^3 x_i^2 \mathbb{P}(X=x_i)

    The variance is \mathbb{E}(X^2)-[\mathbb{E}(X)]^2

    That's all folks
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  3. #3
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    Quote Originally Posted by Moo View Post
    Compute \mathbb{E}(X)=\sum_{i=1}^3 x_i \mathbb{P}(X=x_i)=0.2 \times 10+0.3\times 20+0.5\times 30

    Complete the table with the values of x^2
    Then compute \mathbb{E}(X^2)=\sum_{i=1}^3 x_i^2 \mathbb{P}(X=x_i)

    The variance is \mathbb{E}(X^2)-[\mathbb{E}(X)]^2

    That's all folks
    i dont quite get where do i go once i do 10x0.2+20x0.3+30x0.5 = 23
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  4. #4
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    Quote Originally Posted by arslan View Post
    i dont quite get where do i go once i do 10x0.2+20x0.3+30x0.5 = 23
    You go and do the second and third things that you were told in post #2.
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