Precision and Accuracy of Measurement

Functions of Standards. Fluorescent standards can be used for three basic functions calibration, standardization, and measurement method assessment. In calibration, the standard is used to check or calibrate Instrument characteristics and perturbations on true spectra. For standardization, standards are used to determine the function that relates chemical concentration to Instrument response. This latter use has been expanded from pure materials to quite complex standards that are carried through the total chemical measurement process (10). These more complex standards are now used to assess the precision and accuracy of measurement procedures. 

Our goals in designing the immersion testing system were (i) to emulate or improve upon operations as specified in the manual immersion test method, (ii) to increase sample throughput, (iii) to improve the precision and accuracy of measurements, (iv) to establish procedures for testing materials in hazardous liquids, and (v) to provide sufficient flexibility to handle different types of specimens and enable future expansion of operations. 

The relative ability of the two techniques to produce comparable data structure is impacted by a number of factors. Clearly, instrumental sensitivity, precision, and accuracy play a role for certain elements. INAA, for instance, reported nickel concentrations below detection in all but one sample in the dataset, PRW209, for which a concentration of 20.9 ppm was measured. Using LA-ICP-MS, a concentration of 20.8 ppm was measured for this same sample. However, this technique was also able to detect measurable concentrations of Ni in all other samples, ranging from 13 to 23 ppm. For other elements, high background noise to signal ratios limit the sensitivity, precision and accuracy of measurement by LA-ICP-MS. This is particularly a problem for two elements... 

Expectations or goals regarding the precision and accuracy of measurements, inferences from data regarding distributions for inputs and predictions of the model. 

The performance of analytical methods based on atomic spectrometry is characterized by Pgures of merit, such as LoDs and limits of quantiPcation (LoQs), linear dynamic range, and precision and accuracy of measurements. 

This success would be impossible without a new methodology of thermochemical studies, based on the third-law method, and without certain additional techniques (such as measurements of the absolute rates of decomposition for powders and melts, and determinations of the molar enthalpies of decompositions in the excess of gaseous product) that have greatly improved the precision and accuracy of measurements and simplified and extended the current thermal methods used to study decomposition kinetics (Table 17.2). 

Due to Hawaii s unique situation, all forms of energy have been expensive. The major escalation in the price of natural gas and other related forms of energy in the 1970 s which generated the massive interest in the precision and accuracy of measurement in the gas industry has been a fact of life for us for decades, and the demands for accurate metering have always been foremost in the policies of The Gas Company. 

Comprehensive reviews of the methods of measurement of thermal properties of grains have been published [28,30,31]. Precision and accuracy of measurement are important factors to consider when a method is considered for possible use. However, the variation in composition, size, and shape of agricultural products precludes the need for accuracies greater than 2%-5%. 

TABLE 41.2 NGAL (Rat, Meso Scale Discovery ) Standard Curve Precision and Accuracy of Measured (Back-Calculated) Values versus Nominal Values... 

The capacity factor k is essentially a corrected retention time (Equation [3.18]) that takes into account variations in mobile phase flow rate and thus provides a more robust indicator of analyte retention for a given combination of stationary and mobile phases. As is a unique property of a given solute A for a given stationary-mobile phase combination, the adjusted (corrected) retention volume V,a (Equation [3.15] (or the corresponding retention time) can be used as a tag for analyte identification. Thus the precision and accuracy of measurement of Vja become important and depend on those of the measurement of flow rate U since in practice retention times rather than volumes are the measured quantities. In response to this limitation of the V,a parameter, the capacity ratio of a solute (k) ) was defined as the ratio of its distribution (partition) coefficient to the phase ratio (Vm/V s) of the column with respect to analyte A ... 

Regarding sensors, what are the precision and accuracy of measurements and why are they important for control ... 

Quantitative IR absorption methods differ somewhat from ultraviolet-visible molecular spectroscopic methods because of the greater complexity of the spectra, the narrowness of the absorption bands, and the instrumental limitations of IR instruments. Quantitative data obtained with older dispersive IR instruments were generally significantly inferior in quality to data obtained with U V-visible spectrophotometers. The precision and accuracy of measurements with modern FTIR instruments, however, is distinctly better than those... 

Lowering the requirements with regard to the precision and accuracy of measurement permits the construction of an instrument of far simpler design. Thus, Vallee (1962) described an ice calorimeter composed entirely of glass and permitting enthalpy measurements with an uncertainty of about 0.5% at a drift of approximately 4.2 J h. ... 

Three major field studies have been conducted to determine the precision and accuracy of measurements made using lead-specific PXRF analyzers. The results of these studies are summarized in McKnight et al. (1989) and... 

---