Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Is this true in probability? P(AUB)' = (P(A) + P(B)) '

  1. Apr 9, 2005 #1
    Please help me with Probability

    is this true in probability? P(AUB)' = (P(A) + P(B)) '

    The question is
    a) Assume that P(A) = 0.4 P(AnB)=0.1 P(A'nB')=0.2
    P(B) = ?
    what i did is:
    P(AUB)= P(A)+P(B)- P(AnB)
    P(AUB)= 0.4 + P(B)-0.1
    P(A'nB')= 0.2 = P(AUB)' :confused: = 0.2 = 1 - (0.4 + P(B)-0.1)
    P(B)= -0.5

    NVM I GOT IT MYSELF
     
    Last edited: Apr 9, 2005
  2. jcsd
  3. Apr 9, 2005 #2
    Only if A and B don't occur at the same time (simultaneously)

    marlon
     
  4. Apr 9, 2005 #3
    what is the formula to manipulate such an expression if they occur at the same time?
     
  5. Apr 9, 2005 #4

    xanthym

    User Avatar
    Science Advisor

    Here is the general form:
    P{A ∪ B} = P{A} + P{B} - P{A ∩ B}


    ~~
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook