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Math Help - Probability question

  1. #1
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    Probability question

    Let X be a random variable with probability mass function given by p(-4) = p(4) = 1/16 and p(2) = p(-2) = 7/16. Let Y = aX+b for a certain a and b.

    Part A asks: For what values of a and b does Y take values in {0,1,2,3,4}?

    Now, I solved this part and got a = +/- .5 and b = 2.

    However, my trouble lies in figuring out the answer to this question:
    Compute the probability mass function of Y for these choices of a and b.
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by clockingly View Post
    Let X be a random variable with probability mass function given by p(-4) = p(4) = 1/16 and p(2) = p(-2) = 7/16. Let Y = aX+b for a certain a and b.

    Part A asks: For what values of a and b does Y take values in {0,1,2,3,4}?

    Now, I solved this part and got a = +/- .5 and b = 2.

    However, my trouble lies in figuring out the answer to this question:
    Compute the probability mass function of Y for these choices of a and b.
    Y=X/2+2

    then you have:

    when x=-4, y=0
    when x=-2, y=1
    when x=2, y=3
    when x=4, y=4

    So the pmf for Y is P(0)=p(-4)=1/16, P(1)=p(-2)=7/16, ...

    RonL
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