Measured quantity value

Closeness of agreement between a measured quantity value and a true quantity value of a measurand [vim]... 

Closeness of agreement between indications or measured quantity values... 

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

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

Precision is the closeness of agreement between indications or measured quantity values obtained by replicate measurements on the same or similar objects under specified conditions. 

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]... 

Closeness of agreement between measured quantity values and a true... 

Error is defined as the difference between the expected (true) value and the value obtained as a result of the determination. Thus, error can be calculated as a measured quantity value minus a reference value [3]. Measurement error is the consequence of the accuracy (as trueness and precision) of the analytical procedure applied for obtaining the measured quantity ... 

Our concept of accuracy involves two additional terms, trueness and bias. CAC/GL 72-2009, in defining accuracy, includes a note that states that when applied to a test method, the term accuracy refers to a combination of trueness and precision. Trueness is defined as the closeness of agreement between the average of an infinite number of replicate measured quantity values and a... 

NOTE 3 Measurement accuracy is sometimes understood as closeness of agreement between measured quantity values that are being attributed to 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. 

Fig. 2 Measurement errors in the Uncertainty Approach. Each measured quantity value is accompanied by plus/ minus measurement uncertainty...

Property of a set of measurement results for a specified measurand, such that the absolute value of the differences of any pair of measured quantity values from two different measurement results is smaller than some chosen multiple of the standard measurement uncertainty of that difference. 

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... 

Measurement error of a measuring instrument or measuring system at a specified measured quantity value. 

Datum measurement error where the specified measured quantity value is zero. 

This concept is illustrated in Fig. 3. For evaluating any production error (or product error), we need a nominal value and the tolerance, as well as the measured quantity value plus/minus the measurement uncertainty. 

In measurement 1, measured quantity value plus/minus measurement uncertainty is fuUy within the tolerance limits. Here no production error is present, the product conforms to the specification. 

In measurement, 2 measured quantity value plus/minus measurement uncertainty is partly out of the tolerance zone. Therefore, it is not sure if there is a production error. It is tmcer-tain that the product fulfills the specification. Measurements shall be carried out with smaller measurement uncertainty. 

In measurement 3, measured quantity value plus/minus tolerance is fully outside the tolerance zone. Therefore, we obey a production error. 

The calibration hierarchy is the sequence of calibrations from a reference to the final measuring system, where the outcome of each calibration depends on the outcome of the previous calibration [13]. This hierarchy requires that for measurements incorporating more than one input quantity in the measurement model (e.g., pH, 7), each input quantity must itself be metrologically traceable. In addition, each measurement and derived quantity is listed with an evaluated uncertainty that captures the uncertainties of the measurements and of the calibration hierarchy. Also, because the propagation of variances is additive, measurement uncertainty increases throughout the calibration hierarchy fiomthe RM (which is ideally a certified reference material aka CRM) to the sample. A statement describing the uncertainty is essential, as a measured quantity value unaccompanied by a measurement uncertainty is not only useless, but it is potentially dangerous because the measured value may be misinterpreted or misused. 

Note 1 For a measurement involving replicate indications, each indication can be used to provide a corresponding measured quantity value. This set of individual measured quantity values can be used to calculate a resulting measured quantity value, usually with a decreased associated measurement uncertainty. 

Note 4 In the Guide to the Expression of Uncertainty in Measurement (GUM), published by the International Organization for Standardization ISO [5], the terms result of measurement and estimate of the value of the measurand or just estimate of the measurand are used for measured quantity value (Figure 7.2). 

---