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Homework Help: Probability question ,Random variables and probability distribution

  1. Nov 8, 2012 #1
    I'm completely lost on this probability problem,

    1. The problem statement, all variables and given/known data

    A Box contains 5 indiscernible CDs.It is known that among them 2 are for children .So in order to find the first children's CD ,they are tested one after the other (successively ),Denote by X the random variable which represents the number of tests until the first children's cd is spotted

    1- List all the possible values of X

    2-Determine the probability distribution of X

    3- Calculate the probability that at least 2 tests were performed

    2. The attempt at a solution

    1- x={1 2 3 4 }
    2- very lost here
    3- I can't solve without part 2

    thank you
    Last edited: Nov 8, 2012
  2. jcsd
  3. Nov 8, 2012 #2


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    Is this a trick question? They're CDs, so you'll never spot a book. :wink:

    You should be able to tell us the probability that X=1.
  4. Nov 8, 2012 #3

    Ray Vickson

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    You should also be able to tell us the probability that X = 2. After that, you should be able to do X = 3 and X = 4.

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