Reference quantity value

Closeness of agreement between the average of an infinite number of replicate measured quantity values and a reference quantity value [VM]... 

Error (of measurement) is the sum of random and systematic errors of one measurement. Since a true value cannot be determined, in practice a reference quantity value is used. Each individual result of a measurement will have its own associated error. 

Measured quantity value minus a reference quantity value [VIM]... 

Trueness The closeness of agreement between the average of a infinite nimber of replicate measure quantity values and a reference quantity value [VIM] Precision closeness of agreement between indications ormeasLFed quantity values obtained by replicate measurements on the same or similar objects under specified conditions [VIM]... 

Accuracy closeness of agreement between a measured quantity value (as a single result) and reference quantity value [3]. 

Qoseness of agreement between the average of an infinite number of replicate measured quantity values and a reference quantity value Note 1 Measurement trueness is not a quantity and thus cannot be expressed numerically, but measures for closeness of agreement are given in ISO 5725 (1994-2005). 

In the Error Approach, where the reference quantity value is known, the aim of the measurement is to determine an estimate of the true value that is as close as possible to that single true value. The deviations from the true value consist of random and systematic errors that have to be treated differently. There are no rules, how systematic and random errors combine to form the total error of any measurement result. Usually, the total error is estimated as an upper limit of the absolute value. This upper limit is sometimes loosely named uncertainty. ... 

In the Uncertainty Approach, where the reference quantity value is not known, the aim of the measurement is not to determine a true value as closely as possible, but to assign an interval of reasonable values to the measmand, based on the assumption that no mistakes have been made in performing the measurement. In this approach, the interval of reasonable values assigned to the measurand cannot be reduced to zero, because of the definitional xmcertainty, which is due to the finite amotmt of detail in the definition of the measurand. 

Figure 1 illustrates the Error Approach. Measured quantity values show an error E to a reference quantity value, the error might change for each measurement, due to the fact that we have a random measurement error component R and a systematic measurement error component S. Errors, e.g., for measuring instruments. 

NOTE 1. A reference quantity value for systematic measurement error is a true quantity value, or a measured quantity value of a measurement standard of... 

NOTE 1. A reference quantity value for a random measurement error is the average that would ensue from an infinite number of replicate measurements of the same measurand. 

Extreme value of measurement error, with respect to a known reference quantity value, permitted by specificatiOTis or regulations for a given measurement, measuring instrument, or measuring system. 

Measurement accuracy is the closeness of agreement between the measured quantity value and the true quantity value of a measurand. VIMS regards accuracy and measurement error as idealized quantities that we may not know exactly [14]. VIMS terminology uses measurement trueness, which is the closeness of agreement between the average of an infinite number of replicate measured quantity values and a reference quantity value, as measured using a CRM [13]. In the absence of a CRM that shares sufficient similarity to the protein of interest, any locally prepared material can only provide insight into precision, not trueness. 

Description Sometimes named conventional true value, which is discouraged. As the true value is not accessible by definition, the best approach to it, the conventional quantity value, is used. The best available estimate of the value should be used. This strategy is often applied for reference material certification, when a reference quantity value is being established. 

Description A reference quantity value can be a true quantity value, in which case it is unknovm, or a conventional quantity value, in which case it is known [25]. 

A reference quantity value with associated measurement uncertainty is usually provided with reference to a material, for example, a certified reference material [25]. 

Description Often reference materials (RMs) carry a reference quantity value, for example, mass fraction of Pb in soil, and are used as quality control material, as calibrator, or for validation purposes. 

Definition Systematic measurement error or its estimate, with respect to a reference quantity value (also called bias). 

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