Help calculating standard deviation

[Hengehold]

To make a long story short, I have raw data from a chrono and am trying to calculate the SD in excell. Anyone else out there familiar with how to do this? I made a formula using =STDEVA(data range)

Is that the correct standard deviation formula? there are multiple to choose from and I am trying to make sure I chose the correct one.

My raw data is:

3015
2999
3011
3006
2988
3004
3010
3019
3005
2989

My calculated SD is 10.2
Does that look correct?

Thanks,

-Trevor

 

[Bob L.]

That's the right formula for calculating SD for a sample, which is appropriate for what we do. 10.2 looks reasonable.

 

[SheepDog]

I prefer using the Mean Absolute Deviation over the Standard deviation model. I'm the odd ball one because standard deviation is the preferred method by most. MAD doesn't require squaring the deviations and then finding the square root to get the answer so it gives slightly closer approximations in large data sets. In small data sets (less than twenty) it is difficult to get repeatable results with either technique. I won't say one is better than the other but MAD works for me in terms of finding an expected deviation from an absolute velocity. I used to use shot to shot deviation rather than deviation from average velocity but I found it was counter productive in the prediction of real life deviations.

 

[jeffreybehr]

My Excel produces 9.7.

 

[Titandriver]

For a speedy calculation I take the ES and divide by 3 - gets pretty close.

 

[SheepDog]

Save even more time, just take the ES and skip the SD.

Well, at least this way your velocities will be within the curve about 99.9999% of the time.

 

[300_whisper]

http://m.wikihow.com/Calculate-Standard-Deviation

I always love math....

Engineers lead the way!!

 

[Hengehold]

Thanks gents.
-T

 

[jepp2]

When I am shooting round robin and cannot use the data from my chrono, I created this spreadsheet to input. It gives exactly the same results as my Chrony. Excel had at least 4 different SD formulas you could choose from.