Results 1 to 4 of 4

Math Help - probability of overweight OR female question

  1. #1
    Member
    Joined
    Jul 2010
    Posts
    99

    probability of overweight OR female question

    Hi, can anyone please help me with this question? I'm quite confused this moment.

    In a certain population, containing an equal number of adult males and females, five percent are overweight. Twenty percent of the overweight are female. One person is selected at random from the population. What is the probability that the person is female OR overweight?

    Should I try to calculate P(Female \cup Overweight) ? If that's what I should aim for, how do I do it? I'm so confused.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by tsang View Post
    Hi, can anyone please help me with this question? I'm quite confused this moment.

    In a certain population, containing an equal number of adult males and females, five percent are overweight. Twenty percent of the overweight are female. One person is selected at random from the population. What is the probability that the person is female OR overweight?

    Should I try to calculate P(Female \cup Overweight) ? If that's what I should aim for, how do I do it? I'm so confused.
    \Pr(F \cup O) = \Pr(F) + \Pr(O) - \Pr(F \cap O).

    From the given data you know that \Pr(F) = 0.5 and you know that \Pr(O | F) = 0.2. From this you should be able to calculate \Pr(F \cap O) and hence complete the calculation of \Pr(F \cup O) = \Pr(F) + \Pr(O) - \Pr(F \cap O).

    If you need more help, please show all your work and say where you get stuck.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Jul 2010
    Posts
    99
    Quote Originally Posted by mr fantastic View Post
    \Pr(F \cup O) = \Pr(F) + \Pr(O) - \Pr(F \cap O).

    From the given data you know that \Pr(F) = 0.5 and you know that \Pr(O | F) = 0.2. From this you should be able to calculate \Pr(F \cap O) and hence complete the calculation of \Pr(F \cup O) = \Pr(F) + \Pr(O) - \Pr(F \cap O).

    If you need more help, please show all your work and say where you get stuck.

    Thanks a lot, I just couldn't work out how to approach before.
    I just wonder about one thing please, how do I know it is P(O/F)=0.2, instead of P(F/O)=0.2? From the question wording, it feels like talking about give overweight is condition, then says the females for overweight is 0.2, so should that be P(F/O)=0.2?
    Thanks a lot.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by tsang View Post
    Thanks a lot, I just couldn't work out how to approach before.
    I just wonder about one thing please, how do I know it is P(O/F)=0.2, instead of P(F/O)=0.2? From the question wording, it feels like talking about give overweight is condition, then says the females for overweight is 0.2, so should that be P(F/O)=0.2?
    Thanks a lot.
    Quite right. My mistake. In which case you use Pr(F|O) = 0.2 and Pr(O) = 0.05 to get Pr(F and O).
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 5
    Last Post: February 10th 2013, 02:11 PM
  2. Replies: 3
    Last Post: November 21st 2011, 11:43 PM
  3. Male and Female Combinations Probability
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: October 7th 2010, 01:30 PM
  4. Probability question involving (A given B type question )
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: November 9th 2009, 09:08 AM
  5. A probability question and an Expectations question
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: January 29th 2006, 06:13 PM

Search Tags


/mathhelpforum @mathhelpforum