Results 1 to 7 of 7

Math Help - Discrete set theory.

  1. #1
    Senior Member
    Joined
    Jan 2007
    Posts
    477

    Discrete set theory.

    this is some kinda of discrete set theory I want help with, heres the question and what I have so far, can someone explain what P(A) is, P(~A^B) and (P^~B)
    also what are the independent variables.

    I've included the questions in a pic, and i've written my work the best I could.

    So
    P(A^B) :: 0.3
    P(A|B) :: 0.5 :: P(A) / P(A^B) , So, P(A) :: 0.5 * 0.3 :: 0.15
    Now, P(~A^~B) :: 0.1 ,or , P(A v B) :: 1 -0.1 :: 0.9 :: P(A) +P(B) - P(A^B) , which gives P(B) is greater than 1.0 , this can't happen!

    please help.
    Last edited by mr fantastic; November 23rd 2011 at 05:32 PM. Reason: Title.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,614
    Thanks
    1581
    Awards
    1

    Re: Discrete set theory. Please help.

    Quote Originally Posted by rcmango View Post
    this is some kinda of discrete set theory I want help with, heres the question and what I have so far, can someone explain what P(A) is, P(~A^B) and (P^~B)
    also what are the independent variables.
    I've included the questions in a pic, and i've written my work the best I could.
    So
    P(A^B) :: 0.3
    P(A|B) :: 0.5 :: P(A) / P(A^B) , So, P(A) :: 0.5 * 0.3 :: 0.15
    Now, P(~A^~B) :: 0.1 ,or , P(A v B) :: 1 -0.1 :: 0.9 :: P(A) +P(B) - P(A^B) , which gives P(B) is greater than 1.0 , this can't happen
    None of this makes any sense.
    I take it that this is about probability?
    What does "::" mean?
    What do you know about the rules of a probability measure?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Senior Member
    Joined
    Jan 2007
    Posts
    477

    Re: Discrete set theory. Please help.

    Quote Originally Posted by Plato View Post
    None of this makes any sense.
    I take it that this is about probability?
    What does "::" mean?
    What do you know about the rules of a probability measure?
    :: means equals =
    ..hmm, if it didn't make any sense i would prefer to wait for someone who can make some sense out it, thanks
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Oct 2009
    Posts
    5,530
    Thanks
    774

    Re: Discrete set theory.

    The following line
    Quote Originally Posted by rcmango View Post
    P(A|B) :: 0.5 :: P(A) / P(A^B)
    looks suspicious because P(A|B) = \frac{P(A \cap B)}{P(B)}.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member
    Joined
    Aug 2011
    Posts
    127

    Re: Discrete set theory.

    This is probability, not set theory. You might conflate the two because P(A) in set theory means "the power set of the set A", whereas here it means "the (prior) probability of event A". You might get more help if you put this in the undergrad probability forum.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,614
    Thanks
    1581
    Awards
    1

    Re: Discrete set theory.

    Quote Originally Posted by Annatala View Post
    This is probability, not set theory. You might conflate the two because P(A) in set theory means "the power set of the set A", whereas here it means "the (prior) probability of event A". You might get more help if you put this in the undergrad probability forum.
    Thank you for responding to this post.
    However, we do not encourage double postings.
    The objection to the OP is that it is really nonstandard notation.
    If posters do not know how to use LaTeX at least they can use standard mathematical notation.

    Frankly, I see no reason to help someone who makes no effort to make his/hers question question readable.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Member
    Joined
    Aug 2011
    Posts
    127

    Re: Discrete set theory.

    No problem. I didn't know if there was a method for sending a post to another forum, or quashing it in one so it can be spawned somewhere more appropriate. I don't expect as many people who do probability on a regular basis would be here rather than there, though the question is simple enough that it's not that relevant.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. discrete math probability theory
    Posted in the Discrete Math Forum
    Replies: 1
    Last Post: October 25th 2010, 01:14 PM
  2. Discrete Probability Theory
    Posted in the Statistics Forum
    Replies: 2
    Last Post: March 17th 2010, 10:11 AM
  3. Discrete Probability Theory
    Posted in the Discrete Math Forum
    Replies: 2
    Last Post: March 17th 2010, 10:11 AM
  4. Discrete mathematics set theory problem!
    Posted in the Discrete Math Forum
    Replies: 3
    Last Post: February 3rd 2010, 09:27 AM
  5. discrete math: graph theory
    Posted in the Discrete Math Forum
    Replies: 2
    Last Post: February 27th 2009, 05:02 AM

Search Tags


/mathhelpforum @mathhelpforum