# Math Help - Standard Deviation

1. ## 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?

Best regards

2. ## 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

3. ## Re: Standard Deviation Help Please

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.