Resolution, precision, accuracy, repeatability: Difference between revisions
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'''Accuracy''' is how far measurements are from their true value | '''Accuracy''' is how far measurements are from their true value | ||
: how you know that true value ''itself'' to more accuracy is a good question, though mostly amounts to more work | : how you know that true value ''itself'' to more accuracy is a good question, though mostly amounts to more work until you figure it's good enough | ||
'''Precision''' is largely about how consistent measurements are | '''Precision''' is largely about how consistent measurements are | ||
: measurements can be very precise but not at all accurate | : measurements can be very precise but not at all accurate | ||
:: e.g. a precision instrument that is not calibrated may be consistently within a very narrow margin (so seemingly precise to that small amount -- but inaccurate to the true value) | |||
:: it may then be that calibration is the only thing keeping it from being a lot more accurate -- OR things may be a lot messier and more complex | :: it may then be that calibration is the only thing keeping it from being a lot more accurate -- OR things may be a lot messier and more complex | ||
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If my multimeter shows me 1.153 volts, it makes it easy to assume its accuracy is three digit's worth (around 0.1%). | If my multimeter shows me 1.153 volts, it makes it easy to assume its accuracy is three digit's worth (around 0.1%). | ||
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Also remember that | Also remember that it is easier to be more precise while being no more accurate. | ||
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A statistica description can be seen as an estimator, and you may get better precision (consistent measurements), but not necessarily better accuracy (closeness to a true value). | A statistica description can be seen as an estimator, and you may get better precision (consistent measurements), but not necessarily better accuracy (closeness to a true value). | ||
Latest revision as of 15:54, 29 March 2024
✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.
Accuracy is how far measurements are from their true value
- how you know that true value itself to more accuracy is a good question, though mostly amounts to more work until you figure it's good enough
Precision is largely about how consistent measurements are
- measurements can be very precise but not at all accurate
- e.g. a precision instrument that is not calibrated may be consistently within a very narrow margin (so seemingly precise to that small amount -- but inaccurate to the true value)
- it may then be that calibration is the only thing keeping it from being a lot more accurate -- OR things may be a lot messier and more complex
Resolution is (usually) the units in which is reported (or controlled)
- resolution often hints at the order of accuracy and/or precision, but this can be misleading
- yet high resolution is also a great way to hint at more accuracy and/or precision than you really have
- e.g. does your 4-digit multimeter always show accurate digits? How would you tell?
Repeatability asks that when you later return to the same true value, how stable your measurement of it is
- this is much like precision, but focuses more on the tool or the machine, than the measurement.
- If repeatability is contrasted with reproducibility, then
- repeatibility is often a "can one person on one instrument get the same measurement again", and
- reproducibility is often a "if you have different operators, and/or different instruments, do they get the same measurement?"
- Resolution and repeatability are also words used when asking how well you can actuate/control something - which also makes things more complex because both the control and the measurement of the result may each have their own precision/accuracy details.