Accuracy vs. Precision

[gunmoney]

This is sort of an odd topic and hope it doesn't devolve into nonsense. It falls in line with the whole mag/clip and bullet/cartridge discussion. The follwing link gives a good break down in scientific terms. http://scidiv.bellevuecollege.edu/Physics/Measure&sigfigs/B-Acc-Prec-Unc.html

The idea is that Accuracy means hitting your "target". Precision means repeatability. Many folks describe a gun as accurate which according to the definition is impossible. For a firearm to be accurate it would be capable of being pointed in any direction and when fired, still hit the bulls eye. The correct term should be precise because while the firearm itself may not be capable of hitting a bullseye on it's own it is capable of hitting the same location over and over, or simply repeatability. Humans are capable of accuracy and precision but not a firearm alone. My point is that two important terms are commonly mis-used and seen as interchangeable in relation to firearms and their use; similar to the perceived clip/magazine interchangeability.

 

[Fish_Scientist]

Here's a good visual representation:


Accuracy and Precision by steven.ranney, on Flickr

I use this in lectures of accuracy vs. precision in my classes. When conducting science, if you're after the "true mean," you want your gear to be as accurate as possible. However, sampling gear is rarely accurate. More often than not, it is precise but not accurate. As a result, we take multiple measurements, then take the mean of those measurements. Often times, we are aware that our gear is precise but biased. This is okay; we can adjust for bias. The problem occurs when readings are all over the place (i.e., neither accurate nor precise). When this occurs, your gear needs to be calibrated!

It comes down to being able to correct for bias. For example, if your groups at the range are always up and to the right (biased high and right), you can correct. However, if your rounds impact the target all over the map, you've got some work to do.

Gunmoney is right, though; accuracy and precision are not interchangeable.

Fish

 

[natman]

I agree with the hitting the target vs hitting the same place, but find the exception about being able to point it any where and still hit the target far fetched.

I would say that an accurate rifle hits at point of aim. A precise rifle shoots tight groups, not necessarily to point of aim.

For hunting I'd take an accurate rifle.

 

[gunmoney]

My point is Natman that a rifle is not capable of accuracy but only precision. Accuracy means purposefully or accidentally achieving a desired result. Calling a firearm accurate is incorrect. A gun has no brain or will, it can not decide where to direct a bullet. Only a human can can achieve hitting a bully eye aided by the precision of a firearm that has a known repeatability. It is the same notion that guns can not kill, only a human can kill. A firearm is built to produce a record-able and repeatable action(precision). A person then exploits those characteristics to achieve a desired result, ie hitting a bulls eye (accuracy). If there ever was an accurate firearm it would be the most valuable ever in existence. Imagine, randomly pointing and pulling the trigger and still hitting exactly where you intend.

 

[zxcvbob]

• An atomic clock with just hour and minutes hand is very accurate, but not precise.
• A $2 wristwatch with hour, minute, and second hands is precise but probably not accurate, so the extra precision is pretty much useless.

 

[Aguila Blanca]

My point is Natman that a rifle is not capable of accuracy but only precision.

A precise rifle with badly adjusted sights will shoot a tight group, but not at the point of aim. It is precise, but not accurate.

Adjust the sights so it shoots a tight group where you aim it, and it is accurate as well as precise.

Don't overcomplicate simple issues.

 

[gunmoney]

I am not sure what you your point exactly is zxcvbob. An atomic clock is very precise but only a human, or a human programed computer can tell it where to begin at. A watch, a clock, or whatever, can not magically know what time it is in our existence. It may keep time perfectly but may not be set to the correct time at all. It takes a human in some capacity to set the correct time, again (accuracy) and then for the device to keep it correct from there (precision). A clock can give an accurate time but it has no conscious knowledge that it is the correct time. It only knows the correct increments that time is measured. So again, an inanimate device is incapable of accuracy, only precision.

 

[gunmoney]

Aguila Blanca, you are incorrect. No matter what you do with the sights the rifle will do the exact same thing. The only difference is that the shooter is now able to exploit the guns precision effectively. The complication is when when terms are not used correctly and then therefore confuses the whole issue. Accuracy has a specific definition as does precision. Just because so many have used them incorrectly interchangeably for so long does not make it right. Back to the clip/magazine issue as a reference. A clip is one thing and a magazine is another, they are not one in the same. The same with accuracy and precision.

 

[MrBorland]

The technical difference between accuracy and precision has been discussed numerous times.

In the end, though, the Rule of Conventional Usage applies: "Accuracy" may be technically misused, but because it effectively conveys to other gunnies what's intended, its conventional use is proper.

It falls in line with the whole mag/clip and bullet/cartridge discussion.

In contrast, "mag/clip" and "bullet/cartridge" can certainly can be incorrectly, because there is, by conventional usage, a difference, and gun folks use them accordingly.

 

[Sarge]

The accuracy component is mechanical and lies within the firearm and ammunition. The precision component is up to the shooter and depends largely on his or her expectations of what they should be able to accomplish- and how hard they are willing to work to achieve it.

 

[Elvishead]

All I got to say is, "put your money were your mouth is, pilgrim!"

 

[gunmoney]

Again, conventional usage or not, Accuracy by specific definition means one thing and Precision by definition mean something else. Just because they are used commonly used incorrectly does not make it right. Please read what I posted and the link I provided. I can post many more links that describe the difference in many different scenarios. If you have a real argument please present it instead of back handed comments. Sarge, I am sorry but your post makes no sense whatsoever. I did not just pull this out of the air to start an argument. So again, if anyone has a valid point or argument I will be happy discuss.

 

[Sarge]

Sarge, I am sorry but your post makes no sense whatsoever. I did not just pull this out of the air to start an argument.

Actually, I'm not arguing; I thought you were looking for input. I don't have any question about what the terms mean or how they apply to firearms.

Now if you'd like to redefine 'tries' as square wooden devices that vehicles travel on, I'll be happy to step aside and let you get on with that.

Best of luck to you.

 

[MrBorland]

My point is that two important terms are commonly mis-used and seen as interchangeable in relation to firearms and their use; similar to the perceived clip/magazine interchangeability.

Please read what I posted and the link I provided. I can post many more links that describe the difference in many different scenarios. If you have a real argument please present it instead of back handed comments.

I and many others are well aware the difference and have been for many years, thank you very much. Even so, someone newly discovers this distinction, posts it and presumes to "inform" the rest of us.

I've never found it a very important or interesting distinction when it comes to guns, so rather than pondering how many angels can dance on the head of a pin, you might try something that hasn't been done before - tell us clearly us why it's a functionally important distinction for shooters. If you can't, you either haven't written effectively, and/or conventional usage is proper.

My point is Natman that a rifle is not capable of accuracy but only precision...

...Please read what I posted and the link I provided.

Yet, the very link you provide, begins...

If a clock strikes twelve when the sun is exactly overhead, the clock is said to be accurate.

At this point, I'm not even sure you have a clear grasp on the point you're trying to make.

 

[gunmoney]

Mr. Borland, please read my response to that very question about the clock(post #7). This is not rocket science, it is simply using terms based on its their definitions and not on what one sounds good at the time. No this is not new, but just like every other mis used term, why not set the record straight. I have described it in detail and answered or responded to everyones questions or comments accordingly. I did not think that a thesis was necessary, it is not like I am claiming that the sky is really green or that you can make gun powder out of jell-o.

http://en.wikipedia.org/wiki/Accuracy_and_precision
http://webphysics.iupui.edu/NH/Projects/TEAMS[2]/err6.htm
http://www.butlercc.edu/engineering/en115/en115_accur_vs_prec.cfm
http://honolulu.hawaii.edu/distance/sci122/SciLab/L5/accprec.html
http://phoenix.phys.clemson.edu/tutorials/ap/index.html
http://www.sphere.bc.ca/test/accuracy.html
http://www.tutelman.com/golf/measure/precision.php

 

[zxcvbob]

I am not sure what you your point exactly is zxcvbob.

It's the best example I could think of that separates accuracy from precision -- With the atomic clock, you know what time it is to the nearest minute. With the cheap watch, you know what time it says to the nearest second (greater precision) but you can't really trust that it is correct (accuracy.)

I'm not convinced that the semantic difference really has anything to do with firearms, other than maybe accuracy == repeatability, and precision doesn't really mean anything (higher power optics?)

 

[gunmoney]

I got you now ZXCVBob. Yes I understand your point and even from there, if you read the last link in my last post it starts to get into "resolution" vs precision. Resolution being like your clock examples; while the atomic clock has a greater precision, the cheap watch has a greater resolution. " Resolution is the fineness to which an instrument can be read."- from the link that I mentioned. Excellent points.

 

[zxcvbob]

BTW, when I said "atomic clock" I was thinking of those radio-controlled wall clocks that sync up with WWVB, not an *actual* atomic clock. Sorry for the confusion.

 

[BGutzman]

WoW, splitting hairs taken to the next level! :barf:

 

[44 AMP]

Again, conventional usage or not, Accuracy by specific definition means one thing and Precision by definition mean something else. Just because they are used commonly used incorrectly does not make it right.

Welcome to the real world. There is a curious parallel here, between "proper" definition and usage in the shooting and non shooting community, of the these terms and the usage of "assault rifle" and "assault weapon".

Note how your choice of, and insistance on the "correct" definition is at odds with the common usage. There is a proper definition of "assault rifle" The anti gunners and media chose to ignore it. They created a term to suit their agenda, and got the general public to accept it as correct.

The shooting public has, for decades, used the term "accuracy" to define the repeatablility of the firearm, ammo, and shooter, to produce small groups. The ability of the same combination to strike a specific point on the target is usually referred to as "aim", or as being "sighted in".

A rifle (for example) that hits dead on the first shot, but all the following shots are scattered is not considered accurate. That first shot is accurate, but the rifle is not.

I think part of the problem might be your choosing a definition for accuracy and precision from a college. Shooting, like many other techincally oriented disciplines uses its own definition of terms, which may not be quite the same as a college/dictionary defintion, or as the defintion in general public usage.

Some terms have multiple definitions. Military definitions can be the same way. One has to consider the frame of reference in order to understand which definition is the "proper" one. All may be technically correct, but only one is proper, for the context.

One simple illustration of this is the word "ram", which means vastly different things depending on context. One thing to someone buillding a computer, another thing to someone raising sheep, another to someone running a hydraulic press, another to somone in a bireme (), etc.....