reposted for reference


Accuracy versus Precision




Pictures, a thousand words, yada, yada, yada.  (The aim-point for all examples below is the "X".)




Low level of precision and low level of accuracy . . .









High level of precision and low level of accuracy . . .









Low level of precision and high level of accuracy . . .










High level of precision and high level of accuracy . . .










Even when using factory loaded ammunition, today's semi-automatic AR-15s can be very accurate and precise.  The 10-shot group pictured below was fired from a semi-automatic AR-15 at a distance of 100 yards.







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Even from a rest a ten-shot group without obvious fliers indicates good breath and trigger control.



 

I have started to cringe when I see others post their 3 or 5 shot groups when I have once again become accustom to seeing your 10 shot precise and accurate shot placement.

Check out the "Quarter" Minute of Angle thread.


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The word consistent expresses the idea shown in the second target more clearly than the word precise.

Here we go.

 

Can you link me to the "Consistent Rifle" subforum please?

Precision and Accuracy are conditions measured as errors, rather than levels of non-error (success).

Systematic Errors - a component of error that remains constant, i.e. precision or levels of precision.

Random Errors - when a measurement is repeated it will generally provide a measured value that is different from the previous value, i.e. accuracy or levels of accuracy.


Consistency is simply describing when something does not change, it does not measure error.

It's right next to the accurate rifle subforum.

From Merriam-Webster's online dictionary:

Accurate: 1:  free from error especially as the result of care <an accurate diagnosis> 2:  conforming exactly to truth or to a standard :  exact <providing accurate color> 3:  able to give an accurate result <an accurate gauge>

Simple Definition of precise: very accurate and exact

Full Definition of precise: 1:  exactly or sharply defined or stated 2:  minutely exact 3:  strictly conforming to a pattern, standard, or convention 4:  distinguished from every other <at just that precise moment>

consistent 1 archaic :  possessing firmness or coherence 2a :  marked by harmony, regularity, or steady continuity :  free from variation or contradiction <a consistent style in painting>

Precise and accurate are synonyms in ordinary usage. We're describing target shooting. There is no good reason to depart from standard English usage to describe the difference between a poorly aimed tight group, a well-aimed tight group, a poorly-aimed loose group, and a well-aimed loose group.

If someone says a shooter or a rifle is consistent, everyone knows what he means. However, not everyone knows about the precise/accurate target shooting convention. That alone is reason enough not to use it when other, better ways to describe the concept using plain English exist. I believe in using the simplest words possible to express an idea. Sometimes technical jargon is necessary, but it's not here.

Accuracy is consistency, no?

in dealing with measuring devices (chemistry)

accuracy is how close to the correct value the device reports the measurement... eg. how well it is made... tight group but off the intended aiming spot

precision is how consistent you the reader of the measuring device reports the value... with successive attempts, do you obtain the same results...you hit the aiming spot, but the group is not tight

in shooting, both accuracy and precision results in a tight group at the desired aiming point

The use of the word "precise" in the pictures of the targets is consistent with both its ordinary meaning and the technical jargon. The usage problem arises mainly with the word "accurate." The third picture does not depict accurate shooting. It depicts one accurate shot. The word "accurate" does not mean shots that are evenly but widely dispersed around their intended target either in common or technical usage. For example, no one would describe a scale that when used 10 times shows the weight of 1 gram as 2,3,2,1,2,3,2,3,3, and 2 grams as accurate. Yet, that is analogous to what the third picture shows. Using the word "accurate" to describe widely but evenly dispersed shots is akin to putting a square peg in a round hole. In my opinion, it's better to just say "evenly dispersed" if that's what you're trying to describe.

Now, if we want to say the third picture does in fact show accurate shooting because it's a reduced high-power target and 6 out of 10 shots are inside the 10-ring, that's another discussion altogether. It's also subjective. It does, however, illustrate the that fact that within the context of shooting, the word "accurate" can mean many things depending on what is being discussed.

Consistent can also mean poor. It gives no reference whatsoever to how close to POA the group is, nor how tight the dispersion is.

 

Example:

My rifle shoots a consistent 6MOA with any ammo. Is that precise? Most would say no. Is that accurate? Depends on where the center of dispersion lies.


Precise and accurate are not synonyms in ordinary usage. If I disagree with someone I wouldn't say, "Your statement is not precise."


Just because you say you aren't wrong doesn't make it true.

Again incorrect.

 

An accurate scale can read 21lbs, 21lbs, 21lbs, etc. a hundred times in a row it is consistent. If the scale only reads whole pounds it isn't precise. If the object weighs 20.69345 pounds, the scale is as accurate as it can be, but not precise. If another scale weighs the same object a hundred times in a row and the average is 20.69345 pounds, but each reading varies wildly from that number, the scale is precise but not accurate or consistent. If yet another scale takes a hundred readings of the same object and every single one of the readings is 22.39876 pounds, the scale is precise, consistent, but not accurate. If a scale reads 20lbs, 21lbs, 22lbs, 23lbs, 20lbs, 21lbs, 22lbs, 23lbs, etc., in a repeating pattern for a hundred readings it is consistent but neither accurate nor precise when weighing the 20.69345lbs object. All three terms are not interchangeable and have different meanings, especially when referring to the process of collecting data.


Accuracy describes POA vs. POI.


Precision describes dispersion.


Consistent describes a predictable pattern.

I can't speak for other fields, but in chemistry and basically all natural sciences fields, Molon has it nailed. The terms used are precision and accuracy, just as he defined them. "Consistency" means nothing in this context.

This isn't his opinion, or my opinion, or anyone's opinion on what these terms mean. They are established definitions, and knowing what they mean can help you maintain clarity, rather than ambiguity by mixing up terms.


Not necessarily.

Not if you're consistently inaccurate.

Maybe we should go back to Molon's photos rather than debating alternative words that may or may not carry the same meaning.

A tightly controlled group that falls entirely within the x ring from a point of aim to the same location is both accurate and precise.  

If all shots fall within a 6" circle, centered at the x ring, which is also the aiming point, then it is technically accurate, but not  precise.  

If all shots are MOA or less, but far off to the side of the point of aim, it is precise but not accurate.

This is a descriptive difference that does matter.  Thank you, Molon.

I am the only poster in this thread who has quoted established definitions from any source. The definitions I quoted match how I have used the terms, including the word consistent. That's not my opinion either. It's what the words mean, according to a well-recognized reference source. As I said before, the way the pictures depict precision is consistent with both the word's ordinary and technical definition. The problem comes mainly from the use of the word accurate to express an idea unrelated to precision. I would be interested in seeing a definition of the word accurate from any authoritative reference that describes what is shown in picture number three.

I'll try to explain it another way. Precision is a necessary predicate for accuracy. Nothing that consistently misses the intended target (the "X" ring in picture three) is accurate, no matter how evenly dispersed the misses are. While it's possible that the rifle is being shot as accurately as it can be given the mechanical components and ammunition being used, that does not make the shooting or the the shooter in picture three "accurate" within the ordinary meaning of the word. The usage problems occur when you try to make two synonyms -- accurate and precise -- mean two completely different things.

As for mathematical definitions, I will quote Random House Webster's College Dictionary:

Accuracy 3. Math. the degree of correctness of a quantity, expression, etc. Compare Precision (def. 4).
Precision 4. Math. the degree to which the correctness of a quantity is expressed. Compare Accuracy (def. 3).

In other words, if you have an object that weighs 1.555 grams and a scale that says it weighs 1.556 grams, that scale is accurate. If you have a scale that only reads out in one kilogram increments, that scale is not precise enough to weigh a 1.555 gram object. Due to that scale's lack of precision, it cannot accurately weigh objects that weigh a few grams. However, not even this mathematical distinction between accuracy and precision has anything to do with picture three.

Regardless, I have not seen a reference source from any field that defines "accurate" consistent with what picture three shows. If one exists, I would like to see it.

Roget's Thesarus says they are. What is your source for saying they are not?

I agree with everything you said, except the part in red. A miss is a miss. There is no such thing as an accurate miss. The fact that your misses are centered around your aiming point doesn't somehow make them become accurate shots.

Sure the misses can be accurate. The mean variance from POA to POI is the measurement of accuracy.

Consider an accuracy guarantee. The mfg'er or seller isn't giving you a guarantee that you'll hit the target every time (precision). He's guaranteeing that his product is capable of an accuracy level within a standard deviation.

A 4MOA or a 1/4MOA guarantee doesn't imply that all shots will be hits, but they'll be within that measurement of the POA.



A 1/2MOA precision guarantee would imply that all shots will be within 1/2MOA of every other shot in the group.

I know of no one that makes a precision guarantee.

That is what makes them accurate and not precise. You missed, but not more than the statistical average of the barrels accuracy capability.

consider a game of darts. Accuracy gets you in each scoring zone. You may not hit the dead spot you were aiming at, but the slight miss still counts as points.

So much semantics.
The nomenclature is irrelevant if the ideas are lost in the actual discussion.

I already explained how they are not with an example sentence.


Any basic statistics course will also show the difference.




 

Who gives a shit, man? Talk about a right fighter.

Other way.
Accuracy = centered around POA.



Precision = tight group.
ETA:


A precision rifle can be accurate if it has precisely adjustable sights.


An accurate rifle can be precise with precision gunsmithing and/or precision ammo.





Get both.



http://www.ar15.com/forums/t_16_4/3838_Precision_is_a_relative_term_afterall___.html&page=1
 

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1. Using the definitions in the OP, rank the shooters -- red, blue, and green -- in order from most accurate to least accurate.

2. Assume the target represents a match. Rank the shooters in the order of their finish, best to worst.

In 1994, the International Organization for Standardization adopted a new definition of accuracy, ISO 5725-1:1994.. This definition acknowledged that accuracy is inextricably linked to precision:

"The general term accuracy is used in ISO 5725 to refer to both trueness and precision."

"The term accuracy was at one time used to cover only the one component now named trueness, but it became clear that to many persons it should imply the total displacement of a result from a reference value, due to random as well as systematic effects."

I'm sure many of you think I'm beating a dead horse. However, I think calling what picture three shows "accuracy" causes unnecessary confusion and does not fit common usage or the modern technical usage of the term. A good example of the confusion comes from a post in this thread where a poster who thought he was advocating for the definition of accuracy shown in picture three correctly observed that barrel makers use the word "accuracy" in their guarantees, not precision. Of course, what barrel makers really offer is a precision guarantee, according to the definition of precise in the OP. The fact that the industry uses the word accuracy to express the idea of a tight group in its product guarantees and that even proponents of the definition of accuracy in the OP struggle with applying that definition in the real world says something about the awkwardness of the usage.

I will note again that I am the only one in this thread that has offered reference sources. All of these references sources back up what I am saying, i.e. picture three does not show accuracy, and accuracy does not exist independently of precision. One poster did post seven links to internet articles. Two of those links acknowledge the ISO definition, one of them defines accuracy consistently with the ISO definition, one uses words consistent with ISO and pictures inconsistent with it, and three use the "old' definition of accuracy. Again, the fact that even the proponents of the notion that accuracy exists independently of precision can't quite get it straight should tell you something about the problems with that idea.

1. Blue, Red, Green.



2. Red, Green, Blue.

Since we're now referencing ISO standards, I will never have another "flier" just an outlier, defined by 3.21 as "A member of a set of values which is inconsistent with the other members of that set." I'll just refer to the outliers as my 3.21's.

I do appreciate that cttb is sticking to his guns on this, and bringing references into the discussion. I still however, believe picture three shows the basic definition of accuracy as it pertains to this particular discussion. It may be a broad "stroke" but it illustrates the point. I do not get confused when I step back and take a look at the post as a whole. I'm not sure what other term he would like to use to describe the results in picture three. How much would that theoretical group have to tighten to become "accurate"?

In my 40 some years of shooting Molon has provided the correct use of these terms as applicable to the shooting sports as I have always known them.



Other definitions, especially ISO which is nothing more than a scam on manufacturers and not a standard of any kind, are not what we are discussing here. So yes, your beating a dead horse in this case.



You may as well compare the shooting that Molon does to the shooting a junkie does. Both are defined as shooting.



 

I agree with cttb.

However, I understand the thread and intent.  

Truly, I feel the hairs aren't worth splitting.

But I also see how Molon is breaking it down for the average shooter that might read or see these terms used.

It's a good read.

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