#31
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I agree. It's already been a long winter here.
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#32
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No, that's accuracy.
These are pretty basic scientific concepts that anybody who took a high school chemistry lab should have been taught. Accuracy means a bathroom scale is always going to say 10 lbs. when a 10 lb. dumbbell is placed on it. Precision means the scale is going to say 10.45, 9.98, 10.23, 9.62 and 10.01 lbs. if you weigh the dumbbell 5 times. These are more precise answers (down to 1/100 of a lb.), but not necessarily very accurate, since the readings are nearly 1/2 lb. off in one case. If the scale says 10.00 lbs. every time, it's precise and accurate. If the scale says 15, 5, 16, 12 and 4, it's neither precise nor accurate.
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"You can get help from teachers, but you are going to have to learn a lot by yourself, sitting alone in a room." --Dr. Seuss |
#33
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Let's throw in some quantum mechanics: the very action of measuring something changes the measurement!
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"You can get help from teachers, but you are going to have to learn a lot by yourself, sitting alone in a room." --Dr. Seuss |
#34
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Part of the problem we're encountering seems to be that different fields use terms differently. I find "consistency" and "bias" to be the less ambiguous terms because "precision" and "accuracy" have informal meanings that don't match their more technical meanings. Actually, I find reliability and validity to be even better, but that's because they're the terms used in my field. Frankly, I wouldn't trust much that my high school chemistry teacher said, but your mileage may vary.
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Bob DeVellis |
#35
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Statistically speaking, the mean distances of all of the dots/shots in the two left diagrams, from their cluster center, are very similar (that is the standard deviations of the shots/dots around each cluster center are very similar) BUT the mean distances of all of the dots/shots from the center of the target are not. The mean center of the cluster of dots/shots in the accurate-labeled diagram IS the target (but the standard deviation is sufficiently large that they are not precise). If the target is the object center then each of the dots/shots in the not accurate-labeled diagram ALL have very large mean distances (though the standard deviation of those dots/shots from each other may not differ from the accurate-labeled diagram). The clustering of the shots/dots, regardless of the accuracy with regards to the center of the target, show that they are definitely NOT random. I'm enjoying the discussion, folks! Phil
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Solo Fingerstyle CDs: Two Steps Forward, One Step Back (2021) One Size Does Not Fit All (2018) I play Crosby, Emerald, Larrivée, Lowden, Rainsong & Tacoma guitars. Check out my Guitar Website. See guitar photos & info at my Guitars page. |
#36
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Well, I generally tune to my Snark, and if it sounds a bit off to me, then I tweak it (which I almost never have to do). Then I just play! I've got enough to concentrate on and worry about just trying to become a better player. Worrying about "how" accurate or "how" precise my tuner "really" is isn't even on my radar...
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Martin 000-28EC '71 Harmony Buck Owens American Epiphone Inspired by Gibson J-45 Gold Tone PBR-D Paul Beard Signature Model resonator "Lean your body forward slightly to support the guitar against your chest, for the poetry of the music should resound in your heart." -Andrés Segovia |
#37
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I received a better explanation in college in an aerial photo interpretation course. The instructor had worked for the military doing intelligence work on surveillance photos taken by U-2s and the like. We learned about accuracy, precision, degrees of confidence, etc. http://en.wikipedia.org/wiki/Words_o...ve_probability
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"You can get help from teachers, but you are going to have to learn a lot by yourself, sitting alone in a room." --Dr. Seuss |
#38
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The second example would produce 1 minute of angle accuracy and you can predictably know where the next shot will land so you can adjust/calibrate reliably. |
#39
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An example that might work is shooting at a target with a blunderbuss. If the sights are properly aligned, the outcomes will still be widely dispersed because the gun just isn't very consistent. But if the sights are misaligned (does a blunderbuss even have sights?), the results will be both widely dispersed and off-center. The way the terms were used originally, the former would be described as accurate but imprecise (that is, centered around the target but scattered) while the latter would be neither accurate nor precise (scattered and off-center). Now, in normal parlance, it seems like a stretch to call the first instance "accurate" and probably most of us wouldn't use that word in that situation. It's a poor word to describe the extent to which the central tendency of the observations (irrespective of scatter) corresponds to the "target," but it is used to mean that in some situations. Again, I prefer to describe that as "lack of bias" (i.e., a lack of a tendency to be off systematically, irrespective of any random error). It's really just a case of a specialized usage and a general usage of a word conflicting. Kind of like the misunderstanding that might occur when we tell a non-guitarist that we're going to the store to get a new g-string.
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Bob DeVellis |
#40
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A new g-string, two nuts, a strap and a saddle. Just another Friday night.
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"You can get help from teachers, but you are going to have to learn a lot by yourself, sitting alone in a room." --Dr. Seuss |
#41
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Calibration is NOT your desired reference point. Calibration is the process of adjusting your system by comparing to a known value. In this way, "calibration" is the process of adjusting your sites based on how close you are to your target. Or, turning your tuning peg so that the note matches what is being shown on the tuner.
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侘 寂 -- wabi-sabi -- acceptance of transience and imperfection by finding beauty in that which is imperfect, impermanent, and incomplete |
#42
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This is the most succinct way to differentiate "accuracy" and "precision" as commonly used in measurement theory:
Calibration is the process of adjusting the center of the distribution to be closer to the reference point. Simple as pie.
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侘 寂 -- wabi-sabi -- acceptance of transience and imperfection by finding beauty in that which is imperfect, impermanent, and incomplete Last edited by ecguitar44; 01-17-2014 at 12:34 PM. |
#43
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It doesn't need to be so complicated...
Accuracy...deviation from the true value...accepted as bias as well. Precision...variation in repeated measturements...accepted as spread as well. In principle, it is much easier to take a precise instrument and adjust for accuracy. This is a basic method of process development. It is more difficult to take in imprecise instrument and adjust it to give useful, accurate measurements...unless you are willing to take an average of many readings...which is what most inexpensive (and inprecise) instruments do with varying degrees of success. Do not confuse displayed digits or significant figures or measurement resolution...those are all aspects of the measurement instrument...but are not fundamental concepts of error analysis. Hey gang...go back to tuning and playing your guitars! Cheers.
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2012 Taylor GA3-12 2012 Epiphone Les Paul Ukulele 2008 Cort Earth 70e 1975 Fender Stratocaster 2007 Fender Standard Stratocaster 1967 Epiphone Madrid EC-30 "Make every song you sing your favorite tune." |
#44
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You do realize some people take some topics to extremes, right? And the adjuring to go back to playing is completely wasted when there is a good 'discussion' (argument/debate/dispute) going on. |
#45
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Exactly! That's the whole point of forums like this!
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侘 寂 -- wabi-sabi -- acceptance of transience and imperfection by finding beauty in that which is imperfect, impermanent, and incomplete |