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Math Help - Standard Deviation

  1. #1
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    Standard Deviation

    I'm trying to reverse engineer a spreadsheet I got from a guy I know but am out of contact with. It consists of a data set of numbers for prices of highs and lows over a period of years. I am trying to find out how he arrived at what is labeled in his spreadsheet "Dev". I assume that means Deviation or maybe Standard Deviation.

    Example;

    5 numbers one for each year for the high price;
    71.83 ... 81.06 ... 85.56 ... 91.34 ... 94.19

    5 numbers one for each year for the low price;
    62.27 ... 64.69 ... 74.28 ... 76.95 ... 82.09


    Then he calculated the average or I think the mean(?) by using this formula for both the high and the low;

    =SUM(C3:G3)/5

    The actual average or mean for both were;

    High 84.80
    Low 72.06

    Now this is where I am having difficulty. He calculated "Dev" in his spreadsheet by subtracting the high and low and dividing. The formula is; =SUM(K4-L4)/6 which came out to be 2.12.

    My question is where did the 6 come from in the formula above? Is it something to do with the Standard Deviation formula? There are only 5 numbers in each set listed so I am having a hard time figuring where the dividing by 6 comes from?

    Thanks for your help.

    Best regards
    Last edited by mr fantastic; June 29th 2011 at 03:42 AM. Reason: Title.
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  2. #2
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    Re: Standard Deviation Help Please

    I don't recognise what the formula could be,

    I get


    Mean S.D
    High 84.796 8.856208557
    Low 72.056 8.360656673
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  3. #3
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    Re: Standard Deviation Help Please

    Hi, thanks for the reply.

    I think he was trying to somehow get the average of the high and the low.

    The formula of =SUM(K4-L4)/6 would look like;

    84.796 - 72.056 = 12.74

    12.74 / 6 = 2.12

    The whole thing is where did the 6 come from? It has me stumped.

    If it were a 5 I would say ok there are 5 years of data listed so dividing by 5 makes sense.
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