Results 1 to 2 of 2

Math Help - Definition of Conditional Probability [i.e. P (B|A)]

  1. #1
    Member
    Joined
    Jul 2010
    Posts
    85

    Definition of Conditional Probability [i.e. P (B|A)]

    My teacher gave the definition that:

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

    yet it seems to make more sense to first define

    P(B|A) = \frac{n(A\cap B)}{n(A)} where A takes on the role of the sample space and then divide both the top and bottom of the fraction by n(S) and getting:

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

    which by definition of P would yield the equation at the top.

    Does this make sense? Also, can anyone recommend a good probability book that does these kind of derivations?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Jul 2010
    Posts
    85

    Re: Definition of Conditional Probability [i.e. P (B|A)]

    bump
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Motivation for definition of conditional?
    Posted in the Discrete Math Forum
    Replies: 5
    Last Post: October 23rd 2011, 12:29 AM
  2. Replies: 0
    Last Post: July 22nd 2011, 01:39 AM
  3. Conditional Probability using the Law of Total Probability
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: October 7th 2010, 03:01 AM
  4. conditional probability
    Posted in the Advanced Statistics Forum
    Replies: 5
    Last Post: August 12th 2010, 02:38 PM
  5. Continuous probability - conditional probability
    Posted in the Statistics Forum
    Replies: 1
    Last Post: October 1st 2009, 01:21 AM

Search Tags


/mathhelpforum @mathhelpforum