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Math Help - Statistics for A2 students

  1. #1
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    Statistics for A2 students

    hi there, im stuck on this question:
    x 1 2 3 4
    P(X=x) 0.1 0.2 0.4 0.3

    the table shows the distribution of the discrete random variable X, find
    (a) Var(X)
    (b) Var(X^2)
    (c) Var(24x^-1)

    can sum1 please help me, i got exam on wednesday, thanxzz
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  2. #2
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    do you know the formula for variance? and its easier counter part in terms of expected value... use that

    then you need a theorem about variance when it comes to constants and random variables... are you familiar with that
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  3. #3
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    Quote Originally Posted by artvandalay11 View Post
    do you know the formula for variance? and its easier counter part in terms of expected value... use that

    then you need a theorem about variance when it comes to constants and random variables... are you familiar with that
    yh i know the formula for variance its E(x^2) - (E(X))^2, im not familiar with constants and random variables yet, im working on it. is it possible you can show the working out for the second and third part, as i can do the first part.
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  4. #4
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    Quote Originally Posted by teju View Post
    yh i know the formula for variance its E(x^2) - (E(X))^2, im not familiar with constants and random variables yet, im working on it. is it possible you can show the working out for the second and third part, as i can do the first part.
    Construct a probability table for Y = X^2:

    y 1 4 9 16
    P(Y=y) 0.1 0.2 0.4 0.3

    Now calculate Var(Y) just just like you calculated Var(X) in the first part.


    Construct a probability table for W = 24x^-1 and calculate Var(W) just like you calculated Var(X) in the first part.
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