Accuracy and Precision - yet again

[mikemyers]

I like Murf's signature. Maybe that's all we need:

Accuracy: a whole bunch of holes real close together exactly where you want them to go.

 

[Ed Ames]

that is why i used "alignment", in stead of "adjustment" in my equation.

OK, that makes sense then.

Using the ISO terminology, Group size (precision) + aiming error/sight alignment (trueness) = accuracy.

In other equally valid parlance, the bullet will fall somewhere in the zone defined by group size (precision) + aiming error (accuracy).

 

[murf]

ed ames,

so, what is your opinion on including inherent (fixed) errors in the "precision" side of the equation?

murf

 

[Ed Ames]

ed ames,

so, what is your opinion on including inherent (fixed) errors in the "precision" side of the equation?

murf

Precision would deal with random errors. A fixed error (as the terminology is used in my world) could typically be accommodated by adjusting the sights, and so generally would not be part of precision.

If you are talking about errors like bullet drop over distance, I would say it was clearly trueness/accuracy.

In the case of something like barrel harmonics or a loose barrel bushing where it is inherent in the gun but random I would tend to call that precision.

 

[murf]

i guess what i am trying to do is differentiate all the errors correctable before the shooter "steps to the line", and put those in the "precision" part of the equation. that would leave errors attributable to environmental factors (wind, mirage, trajectory, etc.) in the "sight alignment" part.

just trying to get a procedure down for accurate shooting, i guess.

murf

 

[Ed Ames]

Half of marksmanship is involved in improving precision of the shooter. Shooting jackets, positions like prone, slings, breath control etc. are all to reduce the "noise" we add on top of whatever randomness the gun itself has. That error is properly part of the precision of the "shooting system" (everything that goes into punching a hole in the target) but not the precision of the gun.

The fact that (short of a machine rest none of us own) all measurements are system measurements that don't isolate the gun makes some of this trickier than it seems like it should be.

 

[murf]

agreed. that is why i was trying to put our equation on a time line to translate it to reality. the plus sign goes where the shooter "steps to the line". precision goes on the past side and sight alignment goes on the future side.

the precision side would include all the prep work necessary before one steps up to the line. the alignment side would include things like final sight adjustment, doping the mirage and wind, adjusting the sling, etc.

just trying to make our little equation useful. although, i don't know if this would help shooters, or just confuse them even more.

murf

 

[mikemyers]

......precision is easy to quantify since it is group size. i agree with your assessment as that is how group size has been measured for as long as i can remember (at least 45 years ago). ....... i think accuracy is easy to quantify. it is simply the score of your target.

From what you and Ed are discussing, maybe you can simplify it. "Precision" is maybe agreed on - group size. For "Accuracy", I would rather see a definition that works anywhere, for any target or application, rather than assuming the target can be scored like a NRA target.

Ed wrote "Group size (precision) + aiming error/sight alignment (trueness) = accuracy."

So, Accuracy = Precision + (____________).

Maybe one of you can make up a list of all the things that are included in "precision", and all the things that are included in whatever name you use for the other entry (that Ed called "aiming error.....".

 

[murf]

nah, i'm going to keep it "sight alignment". when you "step to the line", that is the only factor affecting ones score (the precision part should be taken care of beforehand). shooters need to recognize this and focus on this when they start shooting.

i do like your idea of listing things that affect sight alignment. you, me and everyone else ought to get in on this and start the list. i'll go first:

trigger control - it has the most important affect on sight alignment

murf

 

[Reloadron]

Could we say a good analogy for understanding accuracy and precision is to imagine a shooter shooting a target. If the shooter shoots with accuracy, his aim will always take the bullets close to or into the center of the target. If the shooter shoots with precision, his aim will always take the bullets to the same location which may or may not be close to the center of the target. A good shooter will be both precise and accurate by shooting the bullets the same way each time and each time making it in the center of the target. If we look at it this way precision is a high measure of repeatability and accuracy is then unbiased precision, even as the terms apply to shooting a target. Would that hold true?

Accuracy is a qualitative term where the deviation from accuracy which is bias is a quantitative term. The further from target center the greater the bias. The bias can be measured by the distance from target center, the rings on the target or any number of means but we come up with a number.

As to the points totaled on a target? The only reason for scoring a target is to assign a quantitative or numeric value as to how accurately the shooter shot. That numeric value will distinguish the shooter from other shooters in a match or competition.

Does this make sense and would it hold true?

Ron

 

[Pete D.]

Precision is group size.
Accuracy is putting the group where you want it to be.

Maybe?
Pete

 

[cfullgraf]

If the shooter shoots with accuracy, his aim will always take the bullets close to or into the center of the target.

If the shooter's group is centered on the point of aim, it is accurate even though it may be a large group, otherwise known as poor precision.

If the shooter continues to shoot several groups and all center on the point of aim, it is accurate.

But, without a high level of precision otherwise known as a small group in the shooting world, an accurate group is not desirable if it is large.

You have to look at the terms of accuracy and precision as measurement terms, not absolute measurements. Then there are adjectives such as high or low, good or bad, etc, that quantify precision and accuracy as measurements.

Unfortunately, we as shooters either miss apply the terms or the term "accuracy" is a different measurement from the science/engineering measurement when applied to shooting.

Clear as mud?

 

[mikemyers]

Well, if we start with what Ed suggested:

Total Accuracy = "Group Size" (precision) + "general accuracy" (center of group centered on aiming point).

The trick then, is to identify all the things that contribute to group size, and everything else goes into "general accuracy".

So, which of the following belong in "group size" and which belong in "general accuracy", and what did I leave out?

• Quality of the gun (precision?)
• trigger control (precision?)
• quality of sights (precision?)
• breath control? (precision)
• sight alignment (general accuracy?)
• shooter's eyesight (general accuracy?)
• compensation for wind (general accuracy?)
• ammunition (precision?)
• alignment repeatability of gun components (precision?)
• final sight adjustment (general accuracy?)
• doping the mirage and wind (general accuracy?)
• adjusting the sling (general accuracy?)
• barrel trueness (precision?)
• experience of shooter (general accuracy?)
• lighting, as in ability to see the target (general accuracy?)
• number of shots fired (general accuracy?)

If I try to figure this out from what Ed and Murf have suggested, all the factors that contribute to the overall accuracy will be either those that help with precision, or those that help with centering the group over the aiming point.

 

[JohnKSa]

But that is nonsensical to me.

That's my point. When the statement is simplified so that its actual meaning is clear it is not a statement that provides any useful information.

...just trying to rephrase in a way that may find common ground.

I already understand the difference in the two definitions. I just see that the overwhelming evidence says that except in the context of a discussion like this (one that is concerned with carefully dissecting the meaning of the two concepts), it's not important to make a point of separating them.

There's no misunderstanding created when someone refers to accuracy in terms of group size rifle--people aren't mislead into thinking that the person is really bragging on how easily they are able to adjust the sights to align the POI to POA. They don't wonder why the person is referring to group sizes when that's not a measure of accuracy but a measure of precision.

When someone says that their gun is inaccurate, people don't immediately assume that the problem is that the sights aren't adjusted correctly. They realize that the person is complaining that the gun won't group well.

We refer to group size and accuracy interchangeably all the time and nobody is confused. Except in extremely rare situations (like this thread), nobody chimes in to point out the "error" in such usage. As the posts I linked to earlier demonstrate, that's true even of the very folks who are arguing here that it's critical to keep the two concepts separate.

So what we have here is two concepts that obviously only need to be separated for the purpose of discussions like this--not in normal context. Two definitions that are critically different only when we don't make "reasonable assumptions"--to use your own words.

However this discussion plays out, when it is finally over, the people on both sides of it will go back to talking about accuracy in terms of group size. Everyone will understand what is meant, nobody will be confused, nobody will be misled, and nobody will correct the "error". Only a very few who reside at the absolute pinnacle of pedantism will even notice it.

 

[Jim Watson]

I prefer to look at it like Jeff Cooper said:
"Since the dispersion of the weapon is added to the dispersion of the shooter, it can only be desired that the weapon have no dispersion at all."

And Gil Hebard: Align the sights with each other and with the target. Apply pressure to the trigger so that the alignment is not disturbed until the gun goes off.

I do not agree with all items in your thesaurus exercise above, but it is late and I don't care to discuss them now.

Only a very few who reside at the absolute pinnacle of pedantism will even notice it.

You mean like the Internet Experts who burn up the wires discussing the difference between "clip" and "magazine"

 

[Ed Ames]

That's my point. When the statement is simplified so that its actual meaning is clear it is not a statement that provides any useful information.

That's not what I meant by nonsensical. I actually meant that the way you phrased it didn't make any sense and isn't clear. You said, literally, "...the only remaining error is a measurement of error."

How is a measurement of error error?

I already understand the difference in the two definitions.

In that case it is obvious to you why someone (not me) said that if you aren't going to make a distinction between accuracy and precision you should standardize on the word accuracy.

There's no misunderstanding created when someone refers to accuracy in terms of group size rifle.

There actually is. You it see here on THR all the time whenever someone posts a "help me reduce my group size" post. The first steps are always a series of exercises to determine whether the issue is accuracy or precision. Shoot from a bench, have a more skilled person shoot it, shoot in different lighting, look at this chart of characteristic user errors, shoot on a day without heat haze or gusting winds, change ammo, etc.. If switching from a bullseye stance to a ransom rest doesn't change the group size you have a precision issue which means a whole different path to resolution than if the same switch takes you from a 20" group to a 1/2" group.

I prefer to look at it like Jeff Cooper said:
"Since the dispersion of the weapon is added to the dispersion of the shooter, it can only be desired that the weapon have no dispersion at all."

Which is exactly why I say everyone should start out on a supremely accurate )) gun. Eliminate precision to make accuracy issues as clear as possible. I have said almost exactly the same thing as your quote, though I wasn't paraphrasing cooper so much as paraphrasing my dad paraphrasing cooper.

 

[ATLDave]

After another few dozen posts worth of strident pedantry, I still have not seen or read anything that makes me think there is any shooting context in which any of the proposed distinction would be necessary, or even helpful, to clear communication. Which, after all, is the point of non-poetic language.

 

[mikemyers]

......I still have not seen or read anything that makes me think there is any shooting context in which any of the proposed distinction would be necessary, or even helpful........

When I go to an outdoor range, and take a break while waiting to be able to go out and work with my target, I sometimes watch other shooters. Quite a few are doing and saying things they might not, if they had a better understanding of what we've been talking about in this thread.

• A friend of mine shoots two or three shots which are close together, and then the next shot is several inches away. He's puzzled over what he or the gun did wrong. (I don't know how to explain to him, that if his group size is say, six inches, any shots can fall anyplace within that six inch circle at any time. The two or three shots are no more or less "right" than the next shot, that was in a different location. It's random.)
  
• And then there are the shooters, after a few shots that are off one way or another, who start adjusting the sights, a never ending process.

As to whether understanding this is "helpful" or "necessary", who knows. Maybe they're happier just dealing with things the way they've always done, and they enjoy constantly adjusting the sights. Or, maybe they just know that they are much better than what the target shows, and that the problem is their gun.

I think understanding these things can help make one a better shooter.

 

[MrBorland]

I think understanding these things can help make one a better shooter.

I agree with ATLDave, and said as much (though more bluntly) over 60 posts ago.

If all this helps you be a better shooter, great, but don't get bogged down overanalyzing a concept that, in the practical sense, is pretty straightforward. Quality trigger time pays bigger dividends. Do the fundamentals well and consistently (adjust your sights if necessary), and accuracy and precision will take care of themselves. I've harped on this before. Shooting well's an act of faith.

 

[murf]

mikemyers,

tighten fastners - both
consistent grip - general accuracy
mirage - ga
gun cleaning - both
sight adjustment - both (initial - precision, final - ga)
physical stamina - precision
diet - p
clothing - p

the list is endless.

murf

 

[ATLDave]

mikemeyers, none of that is dependent in any way on a semantic difference between "accuracy" and "precision." Understanding that both shooter and guns contribute error/randomness to where bullets land relative to point of aim is important. Hewing to some particular creed about whether the size of a group measures "accuracy" or "precision" isn't.

 

[gamestalker]

Wow, I can't even begin to answer your question. Way, way too many variables.

Give us one a few specifics, such as shot prone with optics, slow fire at X number of yards.

Or shot with a revolver from 25 yds. slow fire.

Or shot rapid fire with a revolver from 25 yds..,

The options go on and on, so maybe give this thread another try, but with some specifics so we can try to answer with some "accuracy" or "precision", pun intended.

GS

 

[[email protected]]

Accuracy or Precission?

10 shots slow fire 25 yd one hand un-supported. Which is this??

 

[mavracer]

I think understanding these things can help make one a better shooter.

Knowledge is knowing that a tomato is fruit, wisdom keeps you from putting it in fruit salad.

Trying to define weather trigger control affects only the size of the group and not location is nieve, as it can most certianly affect either or both.
The key is knowing how to fix the problem not arguing over what to call the problem.

Which is this??

When you can shoot like that you can call it whatever you like.

 

[Reloadron]

10 shots slow fire 25 yd one hand un-supported. Which is this??

What is it? I would say 100-10X.

I would also call it accuracy as the precision is unbiased.

I would also call it good shooting and cause for a beer when the shootin is done and time for fun.

accuracy: a whole bunch of holes real close together exactly where you want them to go.

Yep, that too. ^^^^^

Ron