Results 1 to 4 of 4

Math Help - AP Statistics probability - binomial distribution

  1. #1
    Newbie
    Joined
    Dec 2009
    Posts
    3

    Question AP Statistics probability - binomial distribution

    At an archaeological site that was an ancient swamp, the bones from 20 brontosaur skeletons have been unearthed. The bones do not show any sign of disease or malformation. It is thought that these animals wandered into a deep area of the swamp and became trapped in the swamp bottom. The 20 left femur bones (thigh bones) were located and 4 of these left femurs are to be randomly selected without replacement for DNA testing to determine gender.

    (a) Let X be the number of the 4 selected left femurs that are from males. Based on how these bones were sampled, explain why the probability distribution of X is not binomial.

    I think that the answer is because they selected them without replacement. but if you have a different answer, please help!

    (b) Suppose that the group of 20 brontosaurs whose remains were found in the swamp had been made up of 10 males and 10 females. What is the probability that all 4 in the sample to be tested are male?

    for this one i did.. (10/20)(9/19)(8/18)(7/17) = .0433 = 4.33%

    (c) The DNA testing revealed that all 4 femurs tested were from males. Based on this result and your answer from part (b), do you think that males were equally represented in the group of 20 brontosaurs stuck in the swamp? Explain.

    here is where im confused!

    (d) Is it reasonable to generalize your conclusion in part (c) pertaining to the group of 20 brontosaurs to the population of all brontosaurs? Explain why or why now.

    confused here toooo!


    This is for my apstatistics class. & it's superrr important. basically could determine if I get a B or C in the classs. please helllp!
    Last edited by mr fantastic; January 6th 2010 at 07:25 PM. Reason: Restored original question.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor matheagle's Avatar
    Joined
    Feb 2009
    Posts
    2,763
    Thanks
    5
    This is wor (without replacement).
    So it's hypergeometric not binomial.
    The probability you computed in part (b) gives some evidence to contradict
    the claim that there 10 male and 10 female dinos.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Dec 2009
    Posts
    3
    so, how do you go about doing C & D?

    and i'm not fimiliar with the term hypergeometric.
    Last edited by mr fantastic; January 6th 2010 at 07:27 PM. Reason: Restored deleted post
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor matheagle's Avatar
    Joined
    Feb 2009
    Posts
    2,763
    Thanks
    5
    Quote Originally Posted by tonycsjr16 View Post
    so, how do you go about doing C & D?

    and i'm not fimiliar with the term hypergeometric.

    the hypergeometric in this case, part b is....

     {{10 \choose 4}{10 \choose 0}\over {20 \choose 4}}={{10! \over 4!6!}\over{20!\over 4!16!}}

    That should come out to the same probability that you obtained.
    YOU are selecting 4 of the 10 males AND 0 of the 10 females.
    FROM a sample space that consists of 20 choose 4 dinos.

     ={(10)(9)(8)(7)\over (20)(19)(18)(17)}
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Probability and binomial distribution?
    Posted in the Statistics Forum
    Replies: 5
    Last Post: January 7th 2010, 06:11 AM
  2. Replies: 1
    Last Post: October 5th 2009, 02:14 AM
  3. Statistics: Joint Probability Distribution Problem
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: October 22nd 2008, 01:28 AM
  4. Statistics Probability Distribution..
    Posted in the Advanced Statistics Forum
    Replies: 9
    Last Post: April 9th 2008, 07:46 AM
  5. [SOLVED] Statistics - Binomial Distribution
    Posted in the Statistics Forum
    Replies: 3
    Last Post: January 24th 2008, 05:51 AM

Search Tags


/mathhelpforum @mathhelpforum