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Math Help - Refresh my Memory: Standard Deviation

  1. #1
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    Refresh my Memory: Standard Deviation

    I vaguely recall a "shortcut" sort of formula for calculating the standard deviation for a population. For example, if theres a yes/no survey and 53% of 1,000 people votes yes, what's the standard deviation from the expectation?

    I recall such a formula from my Stats 1 class years ago. It was something like:

    (Number voting yes / Total votes) + (Number voting no / Number votes) * sqrt(something)
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  2. #2
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    Re: Refresh my Memory: Standard Deviation

    \displaystyle \sqrt{np(1-p)}
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  3. #3
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    Re: Refresh my Memory: Standard Deviation

    Where n is sample size and p is probability of positive respons?
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    Re: Refresh my Memory: Standard Deviation

    Yep!
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  5. #5
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    Re: Refresh my Memory: Standard Deviation

    Thank you!
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