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Math Help - Probability Mass Function Question

  1. #1
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    Probability Mass Function Question

    The P.M.F. (probability mass function) of a discrete random variable X is given by,
    f(x)=c ((x^2)+4), where X = (0,1,2,3), and c is a constant.

    a) Determine value of c.
    b) Find the mean and variance of X.

    Does anyone know how to answer this?
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by abc4616 View Post
    The P.M.F. (probability mass function) of a discrete random variable X is given by,
    f(x)=c ((x^2)+4), where X = (0,1,2,3), and c is a constant.

    a) Determine value of c.
    The total probability should sum to 1, so:

    f(0)+f(1)+f(2)+f(3)=1

    so:

    c{(4)+(5)+(8)+(13)}=1

    Which you should be able to solve.

    b) Find the mean and variance of X.
    mean=sum[ n f(n), n=0,1,2,3]

    variance=sum[ (n-mean)^2 f(n), n=0,1,2,3]

    so you are left with the arithmetic.

    RonL
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