How do you guys calculate?????
When you guys post up your standard deviation, I’ve been presuming you mean AVERAGE deviation, as alot of the results reflect this calculation. STANDARD deviation is a whole different calculation….
Please tell me how you are calculating you numbers . AVERAGE deviation is the difference between each shot, added up and divided by the total shots.
STANDARD deviation will give you about double the AVERAGE deviation.
Savagesam’s string post has some correct SD numbers, then they are incorrect on the next string??!!
Do your chronys calculate the SD for you? If so, they are fucking it up every now and then.
Personally, I think AVERAGE deviation is much more representative of the performance of the rifle…
Have I drunk too much beer??!! 😆
All Replies
Revwarnut,
No typo there. If you go to the link given and enter the numbers “5,10,11,14,14” you will get all those different types of Standard Deviation.
Why they call it “Variance (Standard deviation)” and not just Vairance Deviation, I don’t know. Wikipedia probably has a page of airhead talk about it.
That’s probably a good site to calculate your Standard deviation as it lists other forms that are used in different types of study such as population, marketing, or stocks etc. etc. etc.
The site Pab found apparently calculated just the Population (Standard deviation) and didn’t explain that there are other forms for other studies.
FYI Lurker, your first list has a typo saying Variance = 13.7 instead of 3.7.
Or am I missing something here…??
Great info…. thanks!
1 – put a target 50 meters away
2 – fill up your gun at you usual preasure
3 – make yourself comfortable at your favorite benchrest
4 – fire away… say 30 shots.
5 – check out your group. Theres your consistency. 🙂
Bartender, I wanna buy this man a beer!
😆
Pab. I always just record what it tells me is the S.D. I never actually checked it. How is it wrong? I’ve never double checked the numbers.
BenZin,
You have the modern military approach. The other day while at the range I heard a whole lot of rapid fire from the direction of the pistol range. It continued for a loong time. I surmised that only the military would be shooting like that. After the storm quieted the first vehicle to come by was US Army Military Police. I think the philosophy is, you can’t miss if you put enough energy in one general direction. In police shooting we try not to shoot one hole groups so as to maximize pain. But, many of us strive for the ability to hit the same spot consistently and that is our fun. Happy shooting and don’t let a single corner of your target escape unharmed.
I think all this SD, AD, math stuff si very interesting. But i think i have a better, easier, and way more fun way to check “consistency” on my guns…
1 – put a target 50 meters away
2 – fill up your gun at you usual preasure
3 – make yourself comfortable at your favorite benchrest
4 – fire away… say 30 shots.
5 – check out your group. Theres your consistency. 🙂
For the test string above, probably nothing past the decimal point is significant. For the kind of shot strings people are posting, I agree that one decimal point is fine. It all depends on what the numbers are being used for and how big the sample is.
acourvil,
I just tried removing the rounding off in the last step of my spread sheet program and got the exact same answer of 3.701351105.
Since our deviation is a fairly small number I think just one decimal point is adequate. What do you think?
Yup, reckon you are right Lurker. Looks like the one you linked me to is easy enough to use. 😀
Pab,
I really think the calculator site you are using is giving Population Standard Deviation. That’s really close to what I listed above of 3.31059.
You know, I didn’t like Statistics Class because they come up with so many different ways to calculate an average. The key is coming up with the formula that best suites the situation. I think the Population Standard Deviation has to do with people statistics. That is apparently the method used by the site Pab found. Acourvil’s HP-12c calculator confirms my calculation and the web site calculator of http://easycalculation.com/statistics/standard-deviation.php while using “Standard deviation” and non of the others.
That gives me 3.7 for the example that lurker posted and no brain cells used.
I can email you a blank excell spread sheet I use and if you dont have excell – Openoffice.com for a free version.
I like ‘no brain cells used’ 😀
I’ll have a look, ta 😀
pablo – use a spreadsheet and just enter “=STDEV(XY:XZ)” where xy and xz are the starting and ending numbers in your chrony string when entered in a column.
That gives me 3.7 for the example that lurker posted and no brain cells used.
I can email you a blank excell spread sheet I use and if you dont have excell – Openoffice.com for a free version.
My calc gives me SD 3.24 with those numbers. Close to yours, but far enough apart to make a big enough difference over a large set numbers…
The numbers I posted (re the Edgun Matador) were actual standard deviation as calculated by an HP-12c calculator (which shows 3.701351105 as the standard deviation of the string you posted)
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1 – put a target 50 meters away
2 – fill up your gun at you usual preasure
3 – make yourself comfortable at your favorite benchrest
4 – fire away… say 30 shots.
5 – check out your group. Theres your consistency. 🙂
Bartender, I wanna buy this man a beer!
😆
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