Results 1 to 3 of 3

Math Help - The Binomial Distribution errors?

  1. #1
    Junior Member
    Joined
    Jul 2009
    Posts
    49

    The Binomial Distribution errors?

    just thought i would go on a few sites and pratice some Binomial Distribution questions
    i found these on tutorvista , is it me or are all the answers given wrong



    Examples for Application of Binomial Disrtibution:
    Example 1:
    A die is tossed 4 times. What is the Probability of getting exactly 3 fours?
    Solution:
    Here n = 4, x = 3, probability of success on a single trial = 1/ 4 or 0.25.
    Therefore, The binomial probability is,
    p(X =r) = ncr pr q(n-r) where p + q=1 then q =1-p
    q=1-0.25
    q=0.75
    b( 3; 4, 0.25 ) = 4C3 ( 0.25)3 ( 0.75)4 −3
    = ( 4! / 3! (4-3)!) 0.016 ( 0.75)
    = (4! / 3! 1!) 0.016 0.75
    = 4 0.016 0.75
    b( 3; 4, 0.25 ) = 0.048. Answer.
    Example 2:
    A die is tossed 7 times. What is the Probability of getting exactly 5 twos?
    Solution:
    Here n = 7, x = 5, probability of success on a single trial = 1/ 7 or 0.143.
    Therefore, The binomial probability is,
    p(X =r) = ncr pr q(n-r) where p + q=1 then q =1-p
    q=1-0.143
    q=0.857
    b( 5; 7, 0.143 ) = 7C5 ( 0.143)5 ( 0.857)7 −5
    = ( 7! / 5! (7-5)!) (0.0001) ( 0.857)2
    = (7! / 5! 2!) 0.0001 0.734
    = 21 0.0001 0.734
    b( 5; 7, 0.143 ) = 0.00154. Answer.

    Practice Problems for Application of Binomial Distribution:

    1 A die is tossed 2 times. What is the Probability of getting exactly 1sixes?

    1) 0.5.
    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 jickjoker View Post
    just thought i would go on a few sites and pratice some Binomial Distribution questions
    i found these on tutorvista , is it me or are all the answers given wrong



    Examples for Application of Binomial Disrtibution:
    Example 1:
    A die is tossed 4 times. What is the Probability of getting exactly 3 fours?
    Solution:
    Here n = 4, x = 3, probability of success on a single trial = 1/ 4 or 0.25.
    Therefore, The binomial probability is,
    p(X =r) = ncr pr q(n-r) where p + q=1 then q =1-p
    q=1-0.25
    q=0.75
    b( 3; 4, 0.25 ) = 4C3 ( 0.25)3 ( 0.75)4 −3
    = ( 4! / 3! (4-3)!) 0.016 ( 0.75)
    = (4! / 3! 1!) 0.016 0.75
    = 4 0.016 0.75
    b( 3; 4, 0.25 ) = 0.048. Answer.
    Example 2:
    A die is tossed 7 times. What is the Probability of getting exactly 5 twos?
    Solution:
    Here n = 7, x = 5, probability of success on a single trial = 1/ 7 or 0.143.
    Therefore, The binomial probability is,
    p(X =r) = ncr pr q(n-r) where p + q=1 then q =1-p
    q=1-0.143
    q=0.857
    b( 5; 7, 0.143 ) = 7C5 ( 0.143)5 ( 0.857)7 −5
    = ( 7! / 5! (7-5)!) (0.0001) ( 0.857)2
    = (7! / 5! 2!) 0.0001 0.734
    = 21 0.0001 0.734
    b( 5; 7, 0.143 ) = 0.00154. Answer.

    Practice Problems for Application of Binomial Distribution:

    1 A die is tossed 2 times. What is the Probability of getting exactly 1sixes?

    1) 0.5.
    Edit:

    In your first example you have p = 1/4. Is that what the solution said or what the questions said. If the die is fair, then p = 1/6 not 1/4. Similarly on example 2, for a fair die p = 1/6 not 1/7. It looks to me like you should be referencing more competent websites ....

    Practice question: Assuming a fair die, I get 0.2778 (correct to 4dp). Show your working if you want help with why you're wrong.
    Last edited by mr fantastic; February 16th 2011 at 05:19 PM. Reason: Misread the questions.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Jul 2009
    Posts
    49
    example 1 .
    A die is tossed 4 times. What is the Probability of getting exactly 3 fours?
    4c3 = 4 * 0.166 * 0.166* 0.166* 0.833 = 0.01524

    example 2 .
    A die is tossed 7 times. What is the Probability of getting exactly 5 twos?
    7c5 = 21 * 0.166 * 0.166* 0.166 *0.166* 0.166* 0.833 * 0.833 =0.001830

    Practice question:
    2 * 0.166 * 0.833 = 0.2776
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: November 23rd 2010, 03:20 AM
  2. Replies: 3
    Last Post: March 21st 2010, 05:25 PM
  3. Replies: 1
    Last Post: November 12th 2009, 12:38 AM
  4. Replies: 1
    Last Post: March 11th 2009, 11:09 PM
  5. Cumulative distribution function of binomial distribution
    Posted in the Advanced Statistics Forum
    Replies: 2
    Last Post: October 31st 2008, 03:34 PM

Search Tags


/mathhelpforum @mathhelpforum