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Math Help - Variance Help

  1. #1
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    Post Variance Help

    The probability of a manufactured article being in perfect condition is 0.84. The articles are packed in batches of n articles.
    Given that the variance of the number of perfect articles in each batch is 6.72, find the value of n.

    Well i dont seem to get it how to do it, if someone could help would be very appreciated.
    Thank you in anticipation.
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  2. #2
    Moo
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    Hello,

    This problem deals with a binomial distribution...

    we have its expectation equal to np, and its variance equal to np(1-p)
    you have a system of two equations with two unknowns (p and n).
    solve for n
    Last edited by Moo; August 23rd 2009 at 11:55 PM. Reason: spelling
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  3. #3
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    Thank you now i got it
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