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Math Help - Stats/Probability problems

  1. #1
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    Stats/Probability problems

    Thanks ahead of time guys,

    Given P(A) = .3, P(B) = .5, P(A and B) = .2, find
    a) P(A or B)

    b) P(A|B)

    c) P(A with bar on top)

    A single card is drawn from a standard 52 card deck. Let A be the event "the card is a face card" and let B be the event "the card is a red card".
    a) Find P(A) and P(B)

    b) Find P(A|B)

    c) Are A and B independent events? Explain why or why not.

    I'm having troubles understanding these symbols etc. Can anyone somewhat explain the process I have to go through for each problem. Thanks.
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  2. #2
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    what have you tried?

    a) or usually means add the probabilities

    b) P(a|b) = P(a)/P(b)

    c) if an event has a probability of 13% chance of happening then it has an 87% chance of not happening. this is the complement.

    Do you know the definition of a probability?
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  3. #3
    Moo
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    Hello,

    Quote Originally Posted by n00b3 View Post
    what have you tried?

    a) or usually means add the probabilities

    b) P(a|b) = P(a)/P(b)

    c) if an event has a probability of 13% chance of happening then it has an 87% chance of not happening. this is the complement.

    Do you know the definition of a probability?
    This is completely incorrect !!!
    Your formulae are either false, either they do not fit in the situation.

    a) P(A \cup B)=P(A)+P(B)-P(A \cap B)

    where \cup means "or" and \cap means "and"

    b) P(A|B)=\frac{P(A \cap B)}{P(B)}

    c) P(\bar A)=1-P(A)

    If you draw a diagram, most of the answers will fall out from it.
    Last edited by Moo; June 11th 2008 at 09:44 AM. Reason: math tag missing - takk Mr F :D
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