Results 1 to 4 of 4

Math Help - Probability

  1. #1
    Newbie
    Joined
    Feb 2007
    Posts
    2

    Probability

    Could anyone help me with this by any chance... I am sure it is not that dificult for most people but I am really strugling ...

    If 10% of the adult population are without debt at a particular time and a random sample of 20 people are chosen.

    1. What is the probability distribution of the number of people WITHOUT DEBT?
    2. What is the probability that NO MORE than 2 people are without debt?
    3. What is the probability that at least 2 people are without debt?
    4. How many people would be expected to be without debt?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by Grant Townend View Post
    Could anyone help me with this by any chance... I am sure it is not that dificult for most people but I am really strugling ...

    If 10% of the adult population are without debt at a particular time and a random sample of 20 people are chosen.

    1. What is the probability distribution of the number of people WITHOUT DEBT?
    2. What is the probability that NO MORE than 2 people are without debt?
    3. What is the probability that at least 2 people are without debt?
    4. How many people would be expected to be without debt?
    1. binomial b(n;20,0.1)

    2. p(n<=2)=b(0;20,0.1)+b(1;20,0.1)+b(2;20,0.1)

    3. p(n>=2)=1-p(n<=1)=1-[b(0;20,0.1)+b(1;20,0.1)]

    4. 0.1*20 =2

    RonL
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Feb 2007
    Posts
    2

    Probability

    I do have another question and I hope you can help

    How would I solve questions 2 and 3 without using excel?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by Grant Townend View Post
    I do have another question and I hope you can help

    How would I solve questions 2 and 3 without using excel?
    In your notes or text book you will find:

    b(n;N,p) = (N!/(n!(N-n)!) p^n(1-p)^(N-n),

    so:

    2. p(n<=2)=b(0;20,0.1)+b(1;20,0.1)+b(2;20,0.1)


    b(0;20,0.1) = 20!/(0!)(20!) (0.1)^0 (0.9)^20 = 0.9^20

    b(1;20,0.1) = 20!/(1!)(19!) (0.1)^1 (0.9)^19 = 20*0.1* 0.9^19

    b(2;20,0.1) = 20!/(2!)(18!) (0.1)^2 (0.9)^18 = (20*19/2)*0.1^2* 0.9^18

    Then use your calculator.

    3. can be done in the same sort of way.

    RonL
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: October 10th 2014, 10:02 PM
  2. Replies: 10
    Last Post: January 21st 2011, 12:47 PM
  3. Replies: 3
    Last Post: May 29th 2010, 08:29 AM
  4. Replies: 1
    Last Post: February 18th 2010, 02:54 AM
  5. Replies: 3
    Last Post: December 15th 2009, 07:30 AM

Search Tags


/mathhelpforum @mathhelpforum