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    I have this question that I've been trying to do but I just won't get the same answer as what my teacher gave us, please could someone show me how to they would do this Q :

    The random variable X has the distribution below. Given Var(x)= 0.75, find the values of a and b.

    x= 1 2 3
    P(X=x) = a b a

    Thank you
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    (Original post by rn123)
    I have this question that I've been trying to do but I just won't get the same answer as what my teacher gave us, please could someone show me how to they would do this Q :

    The random variable X has the distribution below. Given Var(x)= 0.75, find the values of a and b.

    x= 1 2 3
    P(X=x) = a b a

    Thank you
    Does a = 0.375 b = .25?

    If so, can you write down straight away what E(X) is?

    Then you need two equations for a and b. One comes from using the variance formula. The other can come from knowing what the probabilities must add up to.
 
 
 
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