Accuracy and Precision - yet again

[eldon519]

If you just found a target with a group on it, if you are willing to make the following two assumptions, you could compute some data from it which might be helpful:
-All shots were fired at the same aiming point
-The aiming point is known (for instance the center of the bullseye might be a good guess [could be wrong though])

Once you do that, if you want to do things the manual way, you could make a grid system on the paper with X-Y coordinates. Measure the X and Y coordinates of each shot and the find the average of the respective X values and the respective Y values. That would find your group center in theory. Depending on how many shots you have fired there, that location will may be more or less certain. 20 shots would be more certain the 3 shots. The difference between the center of your group and the aim point (POI vs POA) is your accuracy.

You could also determine the extremes of the group size or also determine the average radial dispersion from the aiming point you calculated. That would give you an idea of the precision. But that number is relative. As was mentioned, a 10" group could be world record break or absolutely terrible depending on the distance and what it was shot with.

Or you may do all this just to figure out some guy was patterning his shotgun for deer season haha.

 

[Louca]

Accuracy is putting a bullet right where you're aiming.
Precision is putting a bullet right where you're aiming.

For those who do not want to differentiate between the two statements above, please use the first one for those of us who do, since it is correct.

 

[Ankeny]

Gosh, I have shot countless itty bitty groups while doping loads that struck the target a coupe of inches away from the point of aim. I always considered a rifle that shot those little groups to be extremely accurate. Glad to know the results of my shooting were inaccurate. Then again, if I just wanted to hit the paper somewhere so I could measure the groups, I guess I was both accurate and precise.

 

[mavracer]

For those who do not want to differentiate between the two statements above, please use the first one for those of us who do, since it is correct.

I'm sorry I refuse to call it precision when you're hitting someplace other than where you intend.

 

[Ed Ames]

I'm sorry I refuse to call it precision when you're hitting someplace other than where you intend.

Why? Precision says nothing about correctness. If I specify that I want the bore of my rifle to be 0.32957105" that is very precise. It is also completely wrong if my rifle is chambered for 6.5x55. It is wrong, with precision.

Likewise if I want to hit a dime I have propped up on a tree limb 100 yards away, and instead my 10 shots make a dime sized hole in the tree limb, that is precision shooting but it wasn't accurate - my hits were precisely wrong.

 

[Louca]

I'm sorry I refuse to call it precision when you're hitting someplace other than where you intend.

Right, since precision has nothing to do with how far off you are from where you intended to hit (assumed to be the aiming point).

Both of his statements cannot be true since accuracy and precision are not the same thing. My comment says to use his first statement, which is correct.

Lou

 

[Teachu2]

To my way of thinking, precise means consistent - if I do everything the same way every time, the shots will all go to the same spot. This translates to group size, regardless of point of aim.

Accurate means that each shot hits where I want it to. Tight group in the bullseye.

 

[MrBorland]

This thread's giving me a headache.

For one thing, we all know the difference between accuracy and precision, so it seems we're discussing semantics and esoterica - "how many angels on the head of a pin" type of thing - none of which seems to answer the OP's question, which, to be honest, I don't understand anyway. It itself seems based on semantics and esoterica.

 

[Ed Ames]

Maybe the most useful way to avoid headaches is to say that precision is a measure of how much ammo you need to expend to correctly measure accuracy.

 

[Louca]

... so it seems we're discussing semantics and esoterica ... none of which seems to answer the OP's question

As I re-read the responses to the OP, I think he received a LOT of input on the concern he had.

Every time I think I know what "accuracy" and "precision" mean, I end up reading something that makes me wonder if I'm really using the terms correctly.

He is wondering about words and their meaning. His subject is the correct usage of the terms precision and accuracy. And yes, you are very accurate, semantics (the study of meaning) is what will be involved here, and exactly what the OP asked for.

I think it is a great discussion, and one that helps us all to communicate. Hopefully, it is not giving the OP a headache. I would like to hear back from him.

 

[murf]

i'll have to agree with mavracers comment in post #29 because of what ed ames said in post # 30. i don't want to be called a precision marksman for gut-shooting a deer 5 times in 4 seconds. remember, precision says nothing about correctness.

i won't use the word "precision" when discussing shooting performance. i'll use "accuracy" and endeavor to be as accurate as possible shooting each and every shot.

not confused anymore!

murf

 

[mikemyers]

......Since we can have both accuracy and precision apply or pertain to rifle as well as handgun shooting why is this thread in handguns? ....

It's in "handguns" because I never thought to put it in what you just suggested might be a better place. My fault. The people who organize these things can relocate it to a more appropriate place.

I wish I knew yesterday what I'll be thinking tomorrow.....

 

[mikemyers]

As I re-read the responses to the OP, I think he received a LOT of input on the concern he had.........He is wondering about words and their meaning. His subject is the correct usage of the terms precision and accuracy. And yes, you are very accurate, semantics (the study of meaning) is what will be involved here, and exactly what the OP asked for.

I think it is a great discussion, and one that helps us all to communicate. Hopefully, it is not giving the OP a headache. I would like to hear back from him.

You must be a mind-reader, as that is exactly what I was trying to say. I don't exactly have a headache, but close. I'm beginning to think the words mean whatever anyone wants them to mean, which is not a very good conclusion. It makes me reluctant to use either word, because people may or may not understand what I meant, and I may be implying something I did NOT mean.

A few of the explanations make more sense to me than others, but I think it's all sort of useless if we don't all think alike.

Sort of like saying "I enjoy the desert".

 

[mikemyers]

If you just found a target with a group on it, if you are willing to make the following two assumptions, you could compute some data from it which might be helpful:
-All shots were fired at the same aiming point
-The aiming point is ....... the center of the bullseye....

Once you do that, if you want to do things the manual way, you could make a grid system on the paper with X-Y coordinates. Measure the X and Y coordinates of each shot and the find the average of the respective X values and the respective Y values. That would find your group center in theory......

I was going to say something like this yesterday, but didn't want to interrupt things. I think you are completely correct. With nothing more than the target, you could draw a grid over it, and calculate the CEP based on data from all the holes on the target. You would then get the "group size", as well as the mathematical center of all the shots. Neither of those is enough to say how well someone did(n't) do. But it is a perfect mathematical representation of the target data. Along with additional information (shooting distance, purpose, etc.), someone could compare this with other data and decide how good it is(n't).

 

[45_auto]

ISO 5725 and the BIPM International Vocabulary of Metrology (VIM) are your friends. If you don't want to use the same terminology as everyone else in the world, feel free to assign any meaning you desire to the words.

3.7
accuracy:
closeness of agreement between a test result or measurement result and the true value

3.13
precision:
closeness of agreement between independent test/measurement results obtained under stipulated conditions

 

[Ed Ames]

Using accuracy will rarely cause confusion and it is what you actually want. You want the bullets to hit where you aim.

Precision is very useful when you get into the why of what you are doing. E.g. why, when you are sighting in a gun, do you fire a group. Understanding precision makes the why obvious but you don't need to understand. Every reference tells you to fire groups when sighting in so you do (though people who don't understand precision tend to short the group sizes...).

 

[mikemyers]

I could add my own thoughts after reading all the above....

I think what most of you are calling "precision" is the same thing as repeatability. If you, your gun, your ammo, and so on can put multiple shots into the same hole, you have excellent precision, regardless of where on the target that hole is.

If you adjust your point of aim, or adjust the sights, or do whatever it takes so that the shots are on or closely centered around the "bullseye", you then have accuracy.

• By that definition, the CEP targets have nothing to do with accuracy, only precision.
  
• ...and the NRA targets are a measure of accuracy + precision.....

....which implies that "accuracy" by itself is simply a measure of how close the center of all the shots is to the point of aim. In terms of wording and language, that works, but it's not what people think of when you use the word "accuracy".

 

[JohnKSa]

So, according to the consensus, what makes a gun accurate has nothing to do with the gun or ammunition, it is solely a matter of whether the sights are/can be adjusted properly or not.

Take a benchrest rifle that will shoot every bullet in the same hole at 100 yards, adjust the scope so that the rounds hit about 5 inches from the point of aim and it is an inaccurate rifle. Adjust the scope so that the rounds hit right at the point of aim, and now it's an accurate rifle. The precision remained unchanged.

I dunno...

My thoughts are that except in the context of a discussion like this with a bunch of people who think it's important to distinguish between accuracy and precision, it's perfectly fine to talk about accuracy in terms of group size. In fact, I suspect if you poke around, you will find that most of the folks who are arguing that group size isn't the same as accuracy have used the terms interchangeably at some point.

For example, here's a post where someone describes an airgun as "accurate". I think it's safe to say that the intent wasn't to assure a potential buyer that the sights could be adjusted to insure that the POI=POA. It was pretty obviously meant to let the audience know that the gun was capable of shooting small groups.

http://www.thehighroad.org/showpost.php?p=9122252&postcount=22

Here's one that's a real puzzler in that the poster describes AMMUNITION as being accurate. Clearly if the true measure of accuracy is simply insuring that the center of the group coincides with the point of aim (regardless of the group size), it makes no sense at all to try to assert that some kinds of ammunition are better at that than other kinds.

http://www.thehighroad.org/showpost.php?p=9141930&postcount=13

In this post, a person claims that a particular brand of .22LR rifle "dominates accuracy competition". If simply adjusting the POI to the POA (regardless of group size) is accuracy, then any brand with fully adjustable sights is just as accurate as any other.

http://www.thehighroad.org/showpost.php?p=9110669&postcount=3

 

[Ed Ames]

My thoughts are that except in the context of a discussion like this with a bunch of people who think it's important to distinguish between accuracy and precision, it's perfectly fine to talk about accuracy in terms of group size.

There is a reasonable assumption that most people want their sights adjusted so that POI has a close, known relationship to POA. Because of that common desire shared by almost all shooters, precision becomes the primary source of accuracy once human error is excluded.

Which does not mean they are the same.

 

[JohnKSa]

...precision becomes the primary source of accuracy once human error is excluded.

By the definitions espoused in this thread, precision is group size--the ability of a gun/ammo system to put all its shots close together. It is the center of the group that determines whether the group is accurate or not--regardless of the group size.

By those definitions, precision is not a factor in accuracy at all (since it is possible to have accuracy without precision and precision without accuracy) and trying to call it "a primary source of accuracy" is contradictory.

 

[Ed Ames]

Nope, not contradictory, not even a distant relative of contradictory.

Accuracy is the distance between where you wanted the bullet to go (presumably POA or a known position relative to POA) and where it actually goes.

Precision is the radius of the circle within which the bullets fall due to noise in the system (variations in powder charge, barrel resonance, improper crown, bullet differences, etc.).

If you adjust the sights so that POA or a known position relative to POA is the center of the circle within which bullets fall, and you want the bullet to go where you aim the gun, then statistically the difference between where you wanted the bullet to go and where it actually goes will be (ignoring human error) the same as the precision of the shooting system.

This is not because they are the same in concept, but because you have adjusted one to overlap with the other. They have no innate connection but whatever person adjusted the sights manually established a connection.

 

[JohnKSa]

Accuracy is the distance between where you wanted the bullet to go (presumably POA or a known position relative to POA) and where it actually goes.

This is a different definition for accuracy than the one under discussion. You're talking about a SINGLE shot vs. the center of a GROUP of shots.

Of necessity, this definition now incorporates precision (as defined in this thread) because now that we're talking about a single shot instead of the center of a group of shots, we have to include the fact that the lack of precision can move our SINGLE shot around considerably on the target even if a GROUP of shots would be centered on the point of aim.

If you want to talk about single shots, then accuracy and precision are hopelessly interwined.

 

[Ed Ames]

Where did you get single shot from? What I am saying works for a machine gun too.

If you manually adjust the sighting system of a firearm so that POA overlaps with the center of the group the gun actually fires, then the "accuracy of the gun" (average distance between POA and POI) and precision (radius within which bullets actually land/group size) will overlap. This isn't because the two are innately related, and it doesn't change the fact that accuracy is not precision and vice versa. It is because a person adjusted the sights to create an overlap, which is what just about everyone does.

 

[JohnKSa]

Accuracy is the distance between where you wanted the bullet to go ... and where it actually goes.

That is a NEW definition.

Up until now, the definition for accuracy had been the distance of the center of the group from the point of aim. Not the distance between where the bullet went and where you wanted it to go.

If precision and accuracy are both going to be defined by groups (one in terms of group size and the other in terms of the location of the center of the group) then they can be separated. If you start trying to talk about where a single bullet goes, then accuracy and precision become intertwined. Or, if you prefer, you could say they overlap.

 

[Ed Ames]

It isn't a new definition. It is just statistics reduced to the minimal sample size. Accuracy measured by firing a single bullet is valid (to the extent you can have a statistical sampling of one) , just not very accurate (chuckle).

If it makes you feel better, add an 's' somewhere in what I wrote to make a plural. It is not important to the point but it works the same either way so I am OK with it.

The same post has this: "If you adjust the sights so that POA or a known position relative to POA is the center of the circle within which bullets fall, and you want the bullet to go where you aim the gun, then statistically the difference between where you wanted the bullet to go and where it actually goes will be (ignoring human error) the same as the precision of the shooting system."

They don't intertwine and they only overlap if a human adjusted the sights to make them overlap.