Accuracy evaluation standardization

The amount of Co in an ore sample is to be determined using a procedure for which Fe is an interferent. To evaluate the procedure s accuracy, a standard sample of ore known to have a Co/Fe ratio of 10.2 1 is analyzed. When pure samples of Co and Fe are taken through the procedure, the following calibration relationships are obtained... 

The foregoing close agreement of the geometric mean diameter and geometric standard deviation results indicates that accuracy evaluations were made on an absolute scale, and did not refer to some arbitrary scale... 

Despite these modifications there remain a number of well-documented problems with the AM1/PM3 core-repulsion function [37] which has resulted in further refinements. For example, Jorgensen and co-workers have developed the PDDG (pair-wise distance directed Gaussian) PM3 and MNDO methods which display improved accuracy over standard NDDO parameterisations [38], However, for methods which include d-orbitals (e.g. MNDO/d [23,24], AMl/d [25] and AMI [39,40]) it has been found that to obtain the correct balance between attractive and repulsive Coulomb interactions requires an additional adjustable parameter p (previously evaluated using the one-centre two-electron integral Gss, Eq. 5-7), which is used in the evaluation of the two-centre two-electron integrals (Eq. 5-8). 

Accuracy Control sample—evaluate standards as samples ... 

Ghezali S, Laurent Ph, Lea S N, Santarelli G, Bahoura M, Simon E, Weyers S, Szymaniec K, Cognet L and Clairon A 1996 About the accuracy evaluation of the LPTF caesium fountain frequency standard . Conference on Precision Electromagnetic Measurements, Braunschweig (DE),THlB-2... 

Run Acceptance Criteria. Run acceptance criteria are used to accept or reject a run because of its performance. As a consequence, no dehned run acceptance criteria are applicable during method development. Prestudy validation runs are accepted based on the standard curve acceptance criteria. No run can be rejected because of poor performance of a sample during precision and accuracy evaluation all data from prestudy validation runs are reported unless there has been a clearly recognizable error during sample preparation or measurement. Despite the fact that the standard curve must satisfy the criteria described for standard curves above, in-study runs are accepted based primarily on the performance of the QC samples. As stated above in the paragraph on precision and accuracy, the 4-6-30 rule is recommended (i.e., at least four of six QC samples must be within 30% of their theoretical values and at least 50% of the values for each level must satisfy the 30% limit. 

No standard materials with known low concentration of alkoxy were available to Hanson and Smith for careful accuracy evaluations. Typical results obtained with fluid and resin samples are given in Table 93. Relative standard deviation was generally below 20% in routine testing. Detection of = SiOR at 0.001% may be readily accomplished. 

The shear viscosity is a tensor quantity, with components T] y, t],cz, T)yx> Vyz> Vzx> Vzy If property of the whole sample rather than of individual atoms and so cannot be calculat< with the same accuracy as the self-diffusion coefficient. For a homogeneous fluid the cor ponents of the shear viscosity should all be equal and so the statistical error can be reducf by averaging over the six components. An estimate of the precision of the calculation c then be determined by evaluating the standard deviation of these components from tl average. Unfortunately, Equation (7.89) cannot be directly used in periodic systems, evi if the positions have been unfolded, because the unfolded distance between two particl may not correspond to the distance of the minimum image that is used to calculate the fore For this reason alternative approaches are required. 

Before a procedure can provide useful analytical information, it is necessary to demonstrate that it is capable of providing acceptable results. Validation is an evaluation of whether the precision and accuracy obtained by following the procedure are appropriate for the problem. In addition, validation ensures that the written procedure has sufficient detail so that different analysts or laboratories following the same procedure obtain comparable results. Ideally, validation uses a standard sample whose composition closely matches the samples for which the procedure was developed. The comparison of replicate analyses can be used to evaluate the procedure s precision and accuracy. Intralaboratory and interlaboratory differences in the procedure also can be evaluated. In the absence of appropriate standards, accuracy can be evaluated by comparing results obtained with a new method to those obtained using a method of known accuracy. Chapter 14 provides a more detailed discussion of validation techniques. 

Consider the situation when the accuracy of a new analytical method is evaluated by analyzing a standard reference material with a known )J,. A sample of the standard is analyzed, and the sample s mean is determined. The null hypothesis is that the sample s mean is equal to p. 

A standard sample of 57.22% w/w CE was analyzed by placing 0.1011 g in a 100-mL volumetric flask and diluting to volume. Three unknowns were prepared by pipeting 0.250 mL, 0.500 mL, and 0.750 mL of the bulk unknown into separate 50-mL volumetric flasks and diluting to volume. Analysis of the three unknowns gave areas of 15310, 31546, and 47582, respectively. Evaluate the accuracy of this analysis. 

Static performance measurements related to positioner/ac tuator operation are conformity, measured accuracy, hysteresis, dead baud, repeatability, and locked stem-pressure gain. Definitions and standardized test procedures for determining these measurements can be found in ISA-S75.13-1989, Method of Evaluating the Performance of Positioners with Analog Input Signals and Pneumatic Output . 

We have presented a simple protocol to run MD simulations for systems of interest. There are, however, some tricks to improve the efficiency and accuracy of molecular dynamics simulations. Some of these techniques, which are discussed later in the book, are today considered standard practice. These methods address diverse issues ranging from efficient force field evaluation to simplified solvent representations. 

Although the RSF contains matrix-dependent quantities, their variations are damped to some extent by virtue of taking ratios, and in practice the RSF is assumed constant for low concentrations of A (e. g. <1 atom%). It can be evaluated from measurements on a well-characterized set of standards containing A in known dilute concentrations. The accuracy of the method, however, is not as high as in laser-SNMS and XPS. 

The accuracy in RBS results is -3% for areal densities and better than 1% for stoichiometric ratios. This high accuracy is obtained only when all relevant quantities are measured or evaluated carefully. Pitfalls which often prevent RBS from achieving its full accuracy are described elsewhere [3.129]. Calibration can be achieved by measuring standards obtained by either implanting into or depositing on a light element (silicon) a known amount of a much heavier element (e.g. Ta or Sb). 

The purpose of this study is twofold to compare four linear aqueous SEC columns made by Tosoh and Showa Denko in terms of composition and performance and to evaluate the effect of commercial PEO standards on the accuracy and precision of the MW and MWD of polyvinylpyrrolidone (PVP) and NIST PEO standards. In terms of performance, emphasis will be placed on factors not commonly covered by column manufacturers. Successful SEC conditions for PVP in water, in water/methanol, and in dimethylformamide can be found in the literature (8,9,10). This study deals mainly with the effects of column, mobile phase, and PEO standards on the MW and MWD of PVP. 

We will be focusing on the MAD, its standard deviation, and the maximum error each direction when we evaluate the relative accuracies of various model chemisti and composite methods in the course of this chapter. 

The function fni(r) given in the standard tables is usually rapidly varying and is therefore difficult to differentiate numerically. The function Fnl[r) is varying much more slowly, and Eq. 11.78 is hence more convenient as the starting point for the numerical work. The accuracy of this method for evaluating the HF energy is now being tested for the atomic case. 

Irani and Callis (Ref 14) used two parameters of the distribution of ground monocalcium phosphate (which follows the commonly used log normal distribution law) namely, Mg and Og, the geometric mean diameter and the geometric standard deviation, to evaluate the precision and accuracy of electro-formed sieves vs sedimentation as a reference procedure ... 

Up to now (1971) only a limited number of reaction series have been completely worked out in our laboratories along the lines outlined in Sec. IV. In fact, there are rather few examples in the literature with a sufficient number of data, accuracy, and temperature range to be worth a thorough statistical treatment. Hence, the examples collected in Table III are mostly from recent experimental work and the previous ones (1) have been reexamined. When evaluating the results, the main attention should be paid to the question as to whether or not the isokinetic relationship holds i.e., to the comparison of standard deviations of So and Sqo The isokinetic temperature /J is viewed as a mere formal quantity and is given no confidence interval. Comparison with previous treatments is mostly restricted to this value, which has generally and improperly been given too much atention. 

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