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Math Help - Variance question

  1. #1
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    Variance question

    I'm not sure I understand this problem based on what I know of variance. Can someone help?

    Suppose that 85% of all households bought in the last 4 months a product made by the Proctor & Gamble Corporation. If 386 households are selected at random, what is the variance of the number of households that bought in the last 4 months a product made by the Proctor & Gamble Corporation?
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  2. #2
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    Quote Originally Posted by dwhee View Post
    I'm not sure I understand this problem based on what I know of variance. Can someone help?

    Suppose that 85% of all households bought in the last 4 months a product made by the Proctor & Gamble Corporation. If 386 households are selected at random, what is the variance of the number of households that bought in the last 4 months a product made by the Proctor & Gamble Corporation?
    The number of households N in your sample that bought a product from P&G
    has a binomial distribution B(386,0.85). The question is asking what is the
    variance of a random variable with this distribution.

    RonL
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  3. #3
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    Quote Originally Posted by dwhee View Post
    I'm not sure I understand this problem based on what I know of variance. Can someone help?

    Suppose that 85% of all households bought in the last 4 months a product made by the Proctor & Gamble Corporation. If 386 households are selected at random, what is the variance of the number of households that bought in the last 4 months a product made by the Proctor & Gamble Corporation?
    just understand what variance means in the dictionary and u'll figure it out. it seems like the difference of 85% of 386 or i may be wrong cause i didn't check the dictionary yet
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  4. #4
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    Quote Originally Posted by lorenzolama View Post
    just understand what variance means in the dictionary and u'll figure it out. it seems like the difference of 85% of 386 or i may be wrong cause i didn't check the dictionary yet
    Wittgenstein wrote:

    "Whereof one cannot speak, thereof one must be silent"

    Obviously he had not seen your posts on MHF recently

    (please consider this a public rebuke)

    RonL
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