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Math Help - memoryless proprety

  1. #1
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    memoryless proprety

    Show that X enjoys a memoryless property.

    P(X>x1+x2)|P(X>x1) = P(X>x2)


    P(X>x1+x2)|P(X>x1) = P(X>x1+x2 and X>x1)/P(X>x1) = P(X>x1)/P(X>x1) = 1. Hence, P(X>x1+x2) and P(X>x2).

    Is this correct?
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  2. #2
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    Quote Originally Posted by lord12 View Post
    Show that X enjoys a memoryless property.

    P(X>x1+x2)|P(X>x1) = P(X>x2)


    P(X>x1+x2)|P(X>x1) = P(X>x1+x2 and X>x1)/P(X>x1) = P(X>x1)/P(X>x1) = 1. Hence, P(X>x1+x2) and P(X>x2).

    Is this correct?
    No.

    1. The notation for the conditional probability is wrong. It should be Pr(X > x1 + x2 | X > x1).

    2. The calculation is wrong. The correct result is Pr(X > x1 + x2 | X > x1) = Pr(X > x1 + x2)/Pr(X > x1).

    Nothing more can be done unless the distribution for X is given. Is X meant to be a geometric random variable? If so, see Q2 b) in this thread: http://www.mathhelpforum.com/math-he...ee-proofs.html
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