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Probability proof

  1. Jun 20, 2009 #1
    how can i proof that >>>>>> p(A | B') = p(A | B)
    well i tried but i think there is a hole in the solution T.T
    if we said that
    p(A|B)=p(A&B)/p(B)

    p(A|B')= p(A&B')/p(b')

    = p(A) - p(A&B)/1-p(B)


    so0o0o how can i complete it ??
     
  2. jcsd
  3. Jun 20, 2009 #2

    arildno

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    In general, you can't prove that.

    That condition holds ONLY for independent events.

    So, in a particular case, you may demonstrate whether that condition holds or not.

    If it holds, A and B are independent events, if not, A and B are not independent events.
     
  4. Jun 20, 2009 #3
    sorry my bad ,, i forgot to mention that A,B are independent
     
  5. Jun 20, 2009 #4

    HallsofIvy

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    In that case, by definition of "independent", P(A|B)= P(A)= P(A|B').
     
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