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Math Help - probability distribution

  1. #1
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    probability distribution

    A crossword puzzle is published in a newspaper daily . Farah could complete , at average , 3 out of 5 crossword puzzles . Find the probability that in 4 certain weeks , Farah could complete at least 2 crossword puzzles in 3 out of the 4 weeks .




    someone pls help me ..
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  2. #2
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    Ok
    Im no genius but here it goes

    So bassicly he can complete 3 out of every 5 puzzles he does.
    There are 4 weeks we need to work out if he can do 2 puzzles in 3 weeks so the 4 weeks isn't relevant?
    now im gonna find the lowest common denominator
    so this means theres a
    9/15 chance he can do a puzzle
    and a
    10/15 chance needed to do 2/3 puzzles

    that's all i can work out sorry hope i've helped
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  3. #3
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    Quote Originally Posted by mathaddict View Post
    A crossword puzzle is published in a newspaper daily . Farah could complete , at average , 3 out of 5 crossword puzzles . Find the probability that in 4 certain weeks , Farah could complete at least 2 crossword puzzles in 3 out of the 4 weeks .




    someone pls help me ..
    This is my take on it:

    The probability of completing a single crossword puzzle in any given week is 3/5 = 0.6.

    Let X be the random variable number of crossword puzzles completed in a given week.

    X ~ Binomial(n = 5, p = 0.6)

    Calculate P = \Pr(X \geq 2) = 1 - \Pr(X \leq 1).


    Let Y be the random variable number of weeks in which at least two crossword puzzles are completed.

    Y ~ Binomial(n = 4, p = P) (P has been calculated above).

    Calculate \Pr(Y = 3).
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  4. #4
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    Quote Originally Posted by lmcph24 View Post
    Ok
    Im no genius but here it goes

    So bassicly he can complete 3 out of every 5 puzzles he does.
    There are 4 weeks we need to work out if he can do 2 puzzles in 3 weeks so the 4 weeks isn't relevant?
    now im gonna find the lowest common denominator
    so this means theres a
    9/15 chance he can do a puzzle
    and a
    10/15 chance needed to do 2/3 puzzles

    that's all i can work out sorry hope i've helped
    Sorry but this reply is wrong for several reasons, including

    1. The fact that it's "at least 2 crossword puzzles", not 2.
    2. The 4 weeks is relevant.
    3. The calculated probabilities are irrelavent to the question.
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    Quote Originally Posted by mr fantastic View Post
    Sorry but this reply is wrong for several reasons, including

    1. The fact that it's "at least 2 crossword puzzles", not 2.
    2. The 4 weeks is relevant.
    3. The calculated probabilities are irrelavent to the question.
    Im sorry for trying to help as i said
    "Im no genius but here it goes"

    And as you told me please don't double post
    Also
    if hes finding out the probability then what does 3 Pr(Y=3) mean in terms of the probability of something happen. I'm most probably wrong but i'm here to learn so please explain
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  6. #6
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    Quote Originally Posted by lmcph24 View Post
    Im sorry for trying to help as i said
    "Im no genius but here it goes"

    And as you told me please don't double post
    Also
    if hes finding out the probability then what does 3 Pr(Y=3) mean in terms of the probability of something happen. I'm most probably wrong but i'm here to learn so please explain
    If you're not sure how to do a question then don't answer it - leave it for someone who is sure. It's better for question to go unanswered for a while than for the OP to get a quick reply that is wrong.


    I don't know where the following has come from or what you mean by it:
    [snip]if hes finding out the probability then what does 3 Pr(Y=3) mean in terms of the probability of something happen[snip]
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  7. #7
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    this might be really stupid but im willing to make a fool of myself.

    the probability he gets 5 right is 0.07776 and he can do that in 1 way
    4= 0.05184 can be done in 5 ways =0.2592
    3= 0.03456 can be done in 10 ways =0.3456
    2= 0.02304 can be done in 10 ways =0.2304
    1= 0.01536 can be done in 5 ways =0.0768
    0= 0.01024 can be done in 1 way

    opps, didnt mean to send that

    so Probability of two or more =0.91296

    he can get 3 of 4 weeks with 2 or more (0.91296X0.91296X0.91296X0.08704) in 4 ways
    = 0.2649318204

    or maybe you could use binomial probability some how
    Last edited by Surreptitous_Smiles; November 13th 2008 at 03:30 PM. Reason: didnt mean to send
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