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  #16  
Old 01-17-2014, 07:54 AM
ecguitar44 ecguitar44 is offline
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Originally Posted by HHP View Post
Maybe in a symbolic sense, the one labeled "accurate not precise" is neither in a literal shooting sense. More illustrative of accuracy and calibration.
Where are you getting calibration from? Calibration, fundamentally requires a comparison between two sets of measurements.

The diagram is "correct"...although I've seen better pictures that represent the differences between precision and accuracy a bit better.
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  #17  
Old 01-17-2014, 07:56 AM
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If you want a tuner to indicate A440, one that is consistently 1/2 step flat every time you use it will be more accurate and precise than one that is randomly 1/4 step flat or 1/4 step sharp. In the first case, you can calibrate or zero to the desired point of measurement, in the second, you can't.
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Old 01-17-2014, 07:58 AM
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Quote:
Originally Posted by devellis View Post
The "accurate" and "precise" concept refer to bias and consistency (or validity and reliability). An unbiased (accurate) device gives a correct value on average. A precise device gives highly consistent values.

I think the term "bias" might be confounding.

In the diagrams above, an accurate shot pattern would be a bunch of shots that hit all around the center of the target. A precise pattern would be tightly grouped, regardless of where they hit the target.

They are two truly different behaviors, operating in two different and independent "axes".

In the tuner world, it does you no good to have a tuner that can measure and display down to 0.000000Hz, but that only repeatably measures to within +/- 5.000Hz That example is super precise and terribly inaccurate.
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  #19  
Old 01-17-2014, 08:04 AM
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here another similar diagram with more shots and it also uses the term bias (which i agree can have a lot of meanings depending on context). i think hhp's point is that one can adjust for bias, which is the same thought i had.



the really good news is that i'm realizing that my guitar playing is quite accurate! (it's just not very precise )
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  #20  
Old 01-17-2014, 08:05 AM
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Originally Posted by ecguitar44 View Post
Where are you getting calibration from? Calibration, fundamentally requires a comparison between two sets of measurements.

The diagram is "correct"...although I've seen better pictures that represent the differences between precision and accuracy a bit better.
Calibration is your desired reference point. In the case of a tuner, you might use a reference tone like a tuning fork. In a rifle, it would be the target center.

When you sight a rifle, you first achieve accuracy (shots consistently impacting the same point) and then calibrate ( adjust sights to move point of impact to desired point). If you can't get the shots to hit the same point of impact (accurate), you have no way to know how to adjust or calibrate.

Like rifles have adjustments for windage and elevation, tuners have calibration screws or dials.
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  #21  
Old 01-17-2014, 08:07 AM
mchalebk mchalebk is offline
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I don't agree with the usage of the words precision and accurate. According to Merriam-Webster, here are the definitions:

pre·cise
: very accurate and exact
—used to refer to an exact and particular time, location, etc.
: very careful and exact about the details of something

ac·cu·rate
: free from mistakes or errors
: able to produce results that are correct : not making mistakes

The definitions are fairly similar and either would seem to be enough to define what you would want in a tuner. I understand the points being made here, but I take issue with the terminology used.
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  #22  
Old 01-17-2014, 08:09 AM
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Here's the bottom line on this.

If your ear can't tell the difference between a guitar tuned with a strobe tuner and a tuning fork, (insert Snark, Intellitouch, or most other cheap tuners) you don't need a strobe tuner.

You simply can't tell the difference and because perception is reality to you, you will argue the point unendingly.

That has nothing to do with your skill, expertise, knowledge, etc.. But don't think that just because it's your reality that it's true. I play with friends who can tune their guitars and I will hand them my tuner and ask them to tune string x and it will always be off. I first noticed it when I could tune with my Intellitouch and could hear that it was off. That doesn't happen with the one I use now.

I'd trade the ear for a lot more skill at playing but since that won't be happening, don't argue that devices that are not as precise, and admittedly so by the manufacturers own admission, are not needed and are no different that the cheap ones.
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  #23  
Old 01-17-2014, 08:10 AM
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Quote:
Originally Posted by mc1 View Post
here another similar diagram with more shots and it also uses the term bias (which i agree can have a lot of meanings depending on context). i think hhp's point is that one can adjust for bias, which is the same thought i had.



the really good news is that i'm realizing that my guitar playing is quite accurate! (it's just not very precise )
The two diagrams on the left are both neither accurate or precise. They are random and unpredictable. The two on the right are both accurate and the lower right is accurate and calibrated.
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  #24  
Old 01-17-2014, 08:45 AM
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Those diagrams are all a little off. Here is a better example:

Suppose you know for certain that the air temperature is exactly 100.42 deg. F.

An accurate thermometer would read 100.42. An inaccurate one could read, for example, 64.31 deg. F.

A precise thermometer could read the temperature to, say, five decimal places: 100.42000 deg. F. A non-precise thermometer might only say it's 100.

A precise thermometer can be accurate (100.42000) or inaccurate (64.32641).

An accurate thermometer could take five readings, and all would read 100.42. A precise one could take five readings and read 72.57837, 116.47854, 102.03851, 50.23464, and 100.50000.

Accuracy refers to the repeatability of results, even if the results are not very specific. Precision refers to how fine a point your put on the results, right or wrong.
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  #25  
Old 01-17-2014, 08:48 AM
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Quote:
Originally Posted by philjs View Post
In another thread discussing tuners that people use there seems to be quite a bit of confusion about what accuracy is, and the importance of the distinction between accuracy and precision. I thought this was important so am posting this as a new thread...this image should help:



A tuner should be both accurate AND precise. To my mind, there are very few tuners that are both...and those that are are strobe tuners.

Phil
Hi philjs...

I'd say strobe tuners are like Gold Medal Winners at the Olympics. Their performance is to be admired, but they have a hard time developing a normal life.

I own 4 strobe tuners, which are rather useless in an ensemble or on even a medium loud stage where one is anywhere near the drummer or bassist. As soon as either hits a note, the guitar picks up their notes and those appear on my tuner screen.

For intonating guitars, strobes are perfect. Also for the solitude of my living room or teaching area. Great in the studio too.

The little charts you present are good, and if you expand the bullseye on the "Both Accurate and Precise" to +-3 cents (3/100 of a ½ step) you allow all the modern electronic tuners. Simpler Electronic tuners are both accurate and precise, but they are calibrated to +-2/100 or +-3/100 of a half step - not +- 1/1000 half step. And if you draw a Bullseye Targed and then draw a center circle which is only 3% of the circle, it will be hard to see (a target with 5 stripes and a circle has the center circle at about 15%) Your little targets have a center which is 33⅓%. +-3cents begins to look more accurate.

I suspect the extreme accuracy and precision of strobes is why Peterson added sweetened tuning capability to it's strobe guitar tuners. They are so accurate that you tune more accurately than you ever have, only to discover your guitar still plays out of tune.

Imagine that, most accurate tuner in the world now assisting us to be less accurate in a precise fashion. Well, when the instrument is built to be not-that-precise, the tuner probably has to adjust as well.

Another factor you did not seem to account for is the quick/slow responsiveness of various tuners.

Some are deliberately slow to pick up on the attack. The initial pluck of a string causes the note to be sharp and then it settles to pitch. This tends to 'unsettle' those who doing the tuning. They don't want to watch strings settle, they want to tune the guitar. Slow in this case doesn't mean faulty, or dull. Sensible…

But with a tuner which is too slow on the initial response, players think it's not working right. Old sweep needle Boss digitals were built that way (first generation).

They quickly countered the slow response by adding a physical needle (first ones just had red arrows with a green middle dot), and it was fun to watch the needle sweep up to pitch. Then when it arrived - it was rock stable since it was desensitized and not prone to jittering.

I personally like a quick response to strings (as with the Snarks) which allows me to cheat and sweeten tunings visually. I just play notes a bit softer and watch for the tendency of the sharpness to decide how sharp, flat, or spot on I want to be.

Interesting discussion....


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  #26  
Old 01-17-2014, 08:52 AM
CrankyChris CrankyChris is offline
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Quote:
Originally Posted by AndrewG View Post
All the accuracy and precision I need is in an A440 tuning fork and my ears.
When you're playing with a band on a stage in front of people that's not very practical.
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  #27  
Old 01-17-2014, 09:01 AM
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Quote:
Originally Posted by devellis View Post
The "accurate" and "precise" concept refer to bias and consistency (or validity and reliability). An unbiased (accurate) device gives a correct value on average. A precise device gives highly consistent values.
This explanation is spot on. In the OP's diagram "bias" is demonstrated in the top left diagram by showing all hits to the NW of the target. However, in the accurate diagram (top right) they are randomly scattered around the target. Precision, on the other hand, is repeatability.
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  #28  
Old 01-17-2014, 09:04 AM
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Your tuner may well be as accurate and precise as it is possible for it to be. Human error in correctly using/reading it is still likely to be a potential problem in many instances.

Keith
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  #29  
Old 01-17-2014, 09:26 AM
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I think the reason the dots seem more closely clustered in the inaccurate, imprecise case than in the accurate imprecise case is that the bulls eye was kind of small. So, to move the loose cluster off center but still have the dots on the bull's eye, they needed to be grouped a bit closer together.

Accuracy in this context really means unbiased. Error is random rather than systematic. Bias in this contexts isn't a prejudicial term. It simply refers to the relationship between the central tendency of the observations and whether or not it corresponds to the true score. The dispersion is centered around the true score in an unbiased (accurate) measurement. In a biased instance, the dispersion is not centered around the true score. That is, even if you control for dispersion through sampling, the result would be biased (i.e., wouldn't converge on the true score).

Precision is just another term for low dispersion or lack of random error. Precision doesn't address whether you're actually measuring what you want to measure but simply that you're measuring something with consistency. If I used a really good light meter to measure pitch, I could get good precision (consistency) but the variable I was consistently measuring would be the wrong one (reflected light, not vibrational frequency of the strings).

Calibration, strictly speaking, is a different parameter. In formal measurement theory, accuracy is measured by the correlation between obtained scores and true scores. If the correlation is very high, the measurement is accurate (or valid). But a high correlation doesn't mean the obtained score and the true score agree. It means they're distributionally similar (i.e., the lowest value for the observed score is the same distance from the average of the observed scores as the lowest value of the true score is from the average of the true scores, and thus for every pair of observed and true scores). This is an error not of precision but of calibration. So, for example, if you assess temperature in Fahrenheit but your criterion reference that provides the true scores is in Celsius, the temperature readings may seldom agree but be perfectly correlated. The Fahrenheit values would be accurate but there would be a calibration discrepancy. A linear transformation of the values form one scale would reproduce the values for the other. In situations where there really is only one measurement scale in play, calibration may not be an issue.
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  #30  
Old 01-17-2014, 09:40 AM
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what he said ^^^ and just to make things worse, if one considers six sigma and anova gage r&r regarding measurement, precision is the resolution of a measurement. accuracy is the ability to reproduce that measurement consistently against a known standard.

precise: an instrument (a tuner for example) manufactured within tight tolerances.

calibration: performance of that instrument validated against a known standard.

accuracy: repeatabliity of said validation to the known standard.

then there is the factors of how someone is using and reading the instrument......

Last edited by arie; 01-17-2014 at 09:47 AM.
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