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Math Help - conditional probability

  1. #1
    Member
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    conditional probability

    Hi,
    I would like some help with this problem

    If X1 and X2 are two discrete random variables with joint probability distribution given by the following bivariate table.(table attached)

    1- Find the probability distributuon of X1

    here I did:
    P(X=0)=0.05+0.15+0.05=0.25
    P(X=1)=0.04+0.1+0.06=0.20
    P(X=2)=...
    P(X=3)=...
    .

    2-Find the conditional probability distribution of X2 given X1=2.
    here I did:
    P(X2|2)=0.08+0.05+0.15
    But I am not sure.

    thank you
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by braddy View Post
    Hi,
    I would like some help with this problem

    If X1 and X2 are two discrete random variables with joint probability distribution given by the following bivariate table.(table attached)

    1- Find the probability distributuon of X1
    here I did:
    P(X=0)=0.05+0.15+0.05=0.25
    P(X=1)=0.04+0.1+0.06=0.20
    P(X=2)=...
    P(X=3)=...
    This is OK just complete the calculation of the marginal distribution

    2-Find the conditional probability distribution of X2 given X1=2.
    here I did:
    P(X2|2)=0.08+0.05+0.15
    But I am not sure.

    thank you
    P(X2=0|X1=2) = 0.08/P(X1=2) = 0.08/0.28 = 0.286
    P(X2=1|X1=2) = 0.05/P(X1=2) = 0.05/0.28 = 0.179
    P(X2=2|X1=2) = 0.15/P(X1=2) = 0.15/0.28 = 0.536

    RonL
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