+ Reply to Thread
Results 1 to 3 of 3

Thread: Can't justify 'correct' answer

  1. #1

    Can't justify 'correct' answer




    I thought I understood sampling without replacement fairly well, but this problem has me stumped as the answer that I calculate doesn't appear to be one of the available choices. The information I have that indicates the 'correct' answer seems wholly inaccurate (ie, I think the correct answer is wrong.).

    A carton holds 18 eggs. If only 3 eggs are fertile, what is the probability of randomly selecting 2 eggs that are fertile if the selected eggs are not replaced?

    A) 3/28
    B) 9/64
    C) 1/4
    D) 3/4

    I was under the impression that the correct answer would be (3/18)*(2/17) = 1/51, but I have reason to believe the 'correct' answer is 1/4.

    Either I'm missing something (Probability > 0.5) or the 'correct' answer is wrong. Is there a justification/formula that indicates the answer is 1/4?

    Thanks for any help anyone can provide.

    Regards,

    John M.

  2. #2
    TS Contributor
    Points: 12,227, Level: 72
    Level completed: 45%, Points required for next Level: 223
    rogojel's Avatar
    Location
    I work in Europe, live in Hungary
    Posts
    1,470
    Thanks
    160
    Thanked 332 Times in 312 Posts

    Re: Can't justify 'correct' answer

    Quote Originally Posted by Brother Maynard View Post
    A carton holds 18 eggs. If only 3 eggs are fertile, what is the probability of randomly selecting 2 eggs that are fertile if the selected eggs are not replaced?

    A) 3/28
    B) 9/64
    C) 1/4
    D) 3/4

    I was under the impression that the correct answer would be (3/18)*(2/17) = 1/51, but I have reason to believe the 'correct' answer is 1/4.

    Either I'm missing something (Probability > 0.5) or the 'correct' answer is wrong. Is there a justification/formula that indicates the answer is 1/4?

    Thanks for any help anyone can provide.

    Regards,

    John M.
    Hi,
    this is a straightforward application of the hypergeometric distribution :
    http://en.wikipedia.org/wiki/Hyperge...c_distribution
    with N=18, K=3, n=2 and k=2 and it will give the same result you got, so I would say the 1/4 is way off the mark (by a factor of 10).

    regards
    rogojel

  3. #3
    Points: 44, Level: 1
    Level completed: 88%, Points required for next Level: 6

    Posts
    2
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: Can't justify 'correct' answer


    Thanks for the prompt reply!

+ Reply to Thread

           




Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts






Advertise on Talk Stats