Looking for information on SD

[ARW]

I have several velocities from my 6BRA but I don't have the SD or ES. How can I calculate my SD and ES from these velocities ?

 

[Micheal]

ES is simply subtracting the lowest velocity from the highest of the group.

2966 fps, 2947 fps, 2978 fps, 2952 fps and 2978 fps would be calculated like this:
2978 fps - 2947 fps = ES: 31 fps

SD is more complicated, the formula can be found online. I’d suggest using one of the many online SD calculators or you can also enter your numbers onto an Excel or Numbers spreadsheet, from there you can use one of the built in formulas to calculate SD.

 

[Webster]

ES is simply subtracting the lowest velocity from the highest of the group.

2966 fps, 2947 fps, 2978 fps, 2952 fps and 2978 fps would be calculated like this:
2978 fps - 2947 fps = ES: 31 fps

SD is more complicated, the formula can be found online. I’d suggest using one of the many online SD calculators or you can also enter your numbers onto an Excel or Numbers spreadsheet, from there you can use one of the built in formulas to calculate SD.

The math gets a little to involved for most of use. I think a simple example some math guy could present to use would be great. Create a group of 5 5 shot groups, 5 powder charges and just show us the results for confidence levels for each group and perhaps some stats on the entire 25 shots. I believe a 90% confidence level just means that 90% of the shots will fall withing 1 STD DEV. 10% of the shots will be outside of 1 STD DEV.

On line SD calculator.

Confidence Interval for a Standard Deviation Calculator

This calculator finds a confidence interval for a population standard deviation, based on input provided by the user.

www.statology.org

 

[Howland]

I have several velocities from my 6BRA but I don't have the SD or ES. How can I calculate my SD and ES from these velocities ?

If you have Excel on a computer, you can insert the formula.

To do it manually, find your average (mean), then find out how much each data point deviates from the average. Add all the deviation values, then divide by however many data points minus one. If you have a ten shot string, divide by nine.

Since SD is a way of estimating the expected variation from the mean of an entire population (all your future shots) by measuring the observed variation of a sample and the larger the sample the better the estimate, I don't even bother calculating SD for five shot groups, I just work with the ES. A ten shot group has some validity. Among statisticians, thirty data points is considered the minimum for a valid SD calculation, but SD from a ten shot group does give you usable information.