# Measurement uncertainty

uncertaintyerroruncertaintiesuncertainty of measurementmeasurement uncertaintiesamount of uncertaintycertaintydegree of uncertaintyerrors of measurementJCGM
In metrology, measurement uncertainty is the expression of the statistical dispersion of the values attributed to a measured quantity.wikipedia
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### Metrology

metrologicalmetrologistlegal metrology
In metrology, measurement uncertainty is the expression of the statistical dispersion of the values attributed to a measured quantity.
Measurement uncertainty is a value associated with a measurement which expresses the spread of possible values associated with the measurand—a quantitative expression of the doubt existing in the measurement.

### Calibration

calibratedcalibratecalibrating
The particular relationship between extension and mass is determined by the calibration of the scale.
This definition states that the calibration process is purely a comparison, but introduces the concept of measurement uncertainty in relating the accuracies of the device under test and the standard.

### Measurement

measuremeasuringmeasured
The purpose of measurement is to provide information about a quantity of interest – a measurand.
However, the following are just some of the sources of error that arise:

### Statistical dispersion

In metrology, measurement uncertainty is the expression of the statistical dispersion of the values attributed to a measured quantity.
Measurement uncertainty

### Joint Committee for Guides in Metrology

International Vocabulary of Metrology
See Joint Committee for Guides in Metrology.
The Guide to the Expression of Uncertainty in Measurement (GUM) is a document published by the JCGM that establishes general rules for evaluating and expressing uncertainty in measurement.

### Probability box

P-boxesbounds on cumulative distributions
Distributions of such measurement intervals can be summarized as probability boxes and Dempster–Shafer structures over the real numbers, which incorporate both aleatoric and epistemic uncertainties.
When those data have non-negligible measurement uncertainty represented by interval ranges about each sample value, an empirical distribution may be generalized to a p-box.

### Standard deviation

standard deviationssample standard deviationsigma
All measurements are subject to uncertainty and a measurement result is complete only when it is accompanied by a statement of the associated uncertainty, such as the standard deviation.

### Mean

mean valuepopulation meanaverage
This particular single choice is usually called the measured value, which may be optimal in some well-defined sense (e.g., a mean, median, or mode).

### Median

averagesample medianmedian-unbiased estimator
This particular single choice is usually called the measured value, which may be optimal in some well-defined sense (e.g., a mean, median, or mode).

### Mode (statistics)

modemodalmodes
This particular single choice is usually called the measured value, which may be optimal in some well-defined sense (e.g., a mean, median, or mode).

### Quantity

quantitiesquantitativeamount
The purpose of measurement is to provide information about a quantity of interest – a measurand.

### Volume

volumetriccapacityvolumes
For example, the measurand might be the size of a cylindrical feature, the volume of a vessel, the potential difference between the terminals of a battery, or the mass concentration of lead in a flask of water.

### Voltage

potential differenceVvoltages
For example, the measurand might be the size of a cylindrical feature, the volume of a vessel, the potential difference between the terminals of a battery, or the mass concentration of lead in a flask of water.

### Mass concentration (chemistry)

mass concentrationw/vmg/dL
For example, the measurand might be the size of a cylindrical feature, the volume of a vessel, the potential difference between the terminals of a battery, or the mass concentration of lead in a flask of water.

### Average

Rushing averageReceiving averagemean
Their average would provide an estimate of the true value of the quantity that generally would be more reliable than an individual measured value.

### ASME

American Society of Mechanical EngineersAmerican Society of Mechanical Engineers (ASME)Fellow
The American Society of Mechanical Engineers (ASME) has produced a suite of standards addressing various aspects of measurement uncertainty.

### ISO/IEC 17025

ISO 17025ISO/IEC 17025:200517025
The GUM has been adopted by all major National Measurement Institutes (NMIs), by international laboratory accreditation standards such as ISO/IEC 17025 General requirements for the competence of testing and calibration laboratories which is required for international laboratory accreditation, and employed in most modern national and international documentary standards on measurement methods and technology.

### International Laboratory Accreditation Cooperation

ILACaccreditedILAC (International Laboratory Accreditation Cooperation)
The GUM has been adopted by all major National Measurement Institutes (NMIs), by international laboratory accreditation standards such as ISO/IEC 17025 General requirements for the competence of testing and calibration laboratories which is required for international laboratory accreditation, and employed in most modern national and international documentary standards on measurement methods and technology.

### Mass

inertial massgravitational massweight
For example, the bathroom scale may convert a measured extension of a spring into an estimate of the measurand, the mass of the person on the scale.

### Mathematical model

modelmathematical modelingmathematical models
A measurement model converts a quantity value into the corresponding value of the measurand.

### Buoyancy

buoyantbuoyant forcefloat
Alternatively, a more sophisticated model of a weighing, involving additional effects such as air buoyancy, is capable of delivering better results for industrial or scientific purposes.

### Temperature

temperaturesair temperaturewarm
In general there are often several different quantities, for example temperature, humidity and displacement, that contribute to the definition of the measurand, and that need to be measured.

### Humidity

humidspecific humidityair humidity
In general there are often several different quantities, for example temperature, humidity and displacement, that contribute to the definition of the measurand, and that need to be measured.

### Displacement (vector)

displacementdisplacement vectordisplacements
In general there are often several different quantities, for example temperature, humidity and displacement, that contribute to the definition of the measurand, and that need to be measured.

### Physical constant

constantconstantsuniversal constant
Some such data relate to quantities representing physical constants, each of which is known imperfectly.