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Math Help - Variance

  1. #1
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    Variance

    In a dozen eggs, the mean number of broken ones is .6
    SD=.5 eggs
    I buy 3 dozen

    I expect to get 1.8 broken eggs.
    Whats the SD?
    I dont understand this...can someone please explain?
    Id really appreciate it!
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by Morgan82 View Post
    In a dozen eggs, the mean number of broken ones is .6
    SD=.5 eggs
    I buy 3 dozen

    I expect to get 1.8 broken eggs.
    Whats the SD?
    I dont understand this...can someone please explain?
    Id really appreciate it!
    The standard deviation scales as the square root of the number of cases.

    There we have a SD of the number of broken eggs for 1 doz of 0.5, so the SD for 3 doz is (0.5)(sqrt(3))~=0.867

    RonL
    Last edited by CaptainBlack; March 13th 2008 at 02:14 PM. Reason: because what it said before was incoherent and wrong at the same time
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  3. #3
    GAMMA Mathematics
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    Quote Originally Posted by Morgan82 View Post
    In a dozen eggs, the mean number of broken ones is .6
    SD=.5 eggs
    I buy 3 dozen

    I expect to get 1.8 broken eggs.
    Whats the SD?
    I dont understand this...can someone please explain?
    Id really appreciate it!
    \sigma_n = \frac{\sigma}{\sqrt{n}} \Rightarrow \frac{1}{2\sqrt{3}} = 0.2887
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