Results 1 to 4 of 4
Like Tree1Thanks
  • 1 Post By Plato

Math Help - Tried this problem and not getting the answer.

  1. #1
    Member
    Joined
    Jan 2009
    From
    Ontario Canada
    Posts
    219

    Lightbulb Tried this problem and not getting the answer.

    Out of 100 customers, 52 buy a shirt, 44 buy a tie and 30 buy both. Determine the probability that a customer who has bought a shirt will also buy a tie?

    ANS = .58.
    So the end it states SHIRT AND TIE?? so it's a multiplication probability?

    I was using P(A and B) = P(A) + P(B) - P(A and B)
    .52 + .44 - (.3) = .66
    BUT MY guess that is wrong. I think it's a two step process. BUT have no clue.

    Any help would be apprecaited. Thanks
    Jo
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Oct 2009
    Posts
    5,501
    Thanks
    765

    Re: Tried this problem and not getting the answer.

    Quote Originally Posted by bradycat View Post
    Determine the probability that a customer who has bought a shirt will also buy a tie?
    Are you asking if you need to determine the probability, as in "Do I really need to determine... ?"?

    Quote Originally Posted by bradycat View Post
    So the end it states SHIRT AND TIE?? so it's a multiplication probability?
    No, it's conditional probability.

    Quote Originally Posted by bradycat View Post
    I was using P(A and B) = P(A) + P(B) - P(A and B)
    The left-hand side should be P(A or B), but this equality is not relevant to this problem. Use the definition of conditional probability: P(A | B) = P(A and B) / P(B). In fact, this is the familiar formula for probability: the number of successful outcomes divided by the total number of outcomes. The difference is that in computing the probability of an event A provided a different event B is known to occur, the sample space (the set of outcomes) is restricted to outcomes in B. Here, instead of all customers, the new sample space consists of only those customers that bought a shirt, and the successful outcomes are those who in addition to a shirt also bought a tie.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,605
    Thanks
    1573
    Awards
    1

    Re: Tried this problem and not getting the answer.

    Quote Originally Posted by bradycat View Post
    Out of 100 customers, 52 buy a shirt, 44 buy a tie and 30 buy both. Determine the probability that a customer who has bought a shirt will also buy a tie?
    ANS = .58.
    You are asked to find P(B|A)=\frac{P(B\cap A)}{P(A)}=\frac{0.3}{0.52}.
    Thanks from bradycat
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Jan 2009
    From
    Ontario Canada
    Posts
    219

    Re: Tried this problem and not getting the answer.

    I was thinking that formula, but thought it was wrong. Thank you for the help. I understand it now.
    The wording for me is tricky, as I have a technology math mind, and this stats sure throws me for a loop on different thinking.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. What is the answer to this problem
    Posted in the Algebra Forum
    Replies: 3
    Last Post: October 31st 2009, 10:24 PM
  2. What would be the answer to this problem?
    Posted in the Algebra Forum
    Replies: 3
    Last Post: October 23rd 2008, 04:14 AM
  3. please show me how to answer this problem
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: November 30th 2007, 03:35 AM
  4. Please check my answer to this problem
    Posted in the Calculus Forum
    Replies: 1
    Last Post: March 20th 2007, 06:04 PM
  5. Replies: 1
    Last Post: February 23rd 2006, 06:15 PM

Search Tags


/mathhelpforum @mathhelpforum