Accuracy through checking

If a check must be made, it must be completely independent. Rather than review a calculation, the calculation must be repeated independently and then compared. If we wanted to really improve the accuracy of orders through checking, we would have two people enter them independently and then compare them. If identical, they would go to the supplier for processing. If they differed, we would find and correct the problem. In the case of promotional products, this is too expensive for the additional accuracy we would achieve. We acknowledge that there are many circumstances in industry where this is necessary. However, in practice, we rarely see inspection carried out in this fashion. What we see is checking, reviewing the calculation made by another worker. This is the worst thing that could be done it will make accuracy worse, not better, and will cost time that could be better spent in other ways. 

Note that in this nonnalized probability, the properties of the reser >oir enter the result only through the common equilibrium temperature T. The accuracy of the expansion used above can be checked by considering the next temi, which is... 

We stop the calculation once the change in the coordinates is thought to be acceptable. In general, convergence is slow and the only way to check the accuracy is to carry through yet another cycle and observe the changes in predicted coordinates. 

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. 

If the sample and standard have essentially the same matrices (e.g., air particulates or river sediments), one can go through the total measurement process with both the sample and the standard in order to (a) check the accuracy of the measurement process used (compare the concentration values obtained for the standard with the certified values) and (b) obtain some confidence about the accuracy of the concentration measurements on the unknown sample since both have gone through the same chemical measurement process (except sample collection). It is not recommended, however, that pure standards be used to standardize the total chemical measurement process for natural matrix type samples chemical concentrations in the natural matrices could be seriously misread, especially since the pure PAH probably would be totally extracted in a given solvent, whereas the PAH in the matrix material probably would not be. All the parameters and matrix effects. Including extraction efficiencies, are carefully checked in the certification process leading to SRM s. 

The equation will be solved under the assumption that the particles in the fluid are interacting through a truncated Lennard-Jones 12-6 potential. The Lennard-Jones potential has been used by several workers, including Khan and Broyles,5 Throop and Bearman,6 and Levesque.7 These workers studied the PY equation above the reduced critical temperature T c in considerable detail. Their results in that region provided a good check on the accuracy of the method described here. 

Standard reference material (SRM) for wavelength accuracy, stray light, resolution check, and photometric accuracy can be purchased from NIST. Certified reference materials (CRMs) which are traceable to NIST and recertification services can be purchased from instrument manufacturers and commercial vendors [12]. The cost of neutral-density filters and prefabricated standard solutions in sealed cuvettes can be substantial. When purchasing performance verification standards from a secondary supplier other than a national standard organizations such as NIST in the United States and National Physical Laboratory (NPL) in the United Kingdom, make sure that the traceability of the standards are available in the certificates. The traceability establishes the relationship of individual results to the national standard through an unbroken chain of comparisons. 

A series of mercury mass balances was obtained at a coal-fired power plant by comparing the volatile and particulate mercury in the stack gas stream to the mercury initially in the coal, corrected for the mercury adsorbed and retained by the various ashes. These data were used to determine the fate of the mercury in the combustion process and to check the accuracy of the volatile mercury sampling procedure (gold amalgamation). The bottom ash had the lowest mercury concentration of the ash samples collected, and the mercury concentration increased as one proceeded through the ash collection system from the initial mechanical ash to the electrostatic ash. The mercury recovered in the various ashes represented about 10% of the total mercury introduced in the raw coal. 

At my suggestion she carried out an experiment to determine for herself whether there was a psi component to her OOBEs. After lying down in bed she would blindly reach into a box containing randomized pieces of paper with the numbers one through ten on them and, without looking, lay one on her bedside table. She could not see it from the bed. If she had an OOBE, she was to memorize the number and check for accuracy in the morning. 

The accuracy of the test procedure was validated by room temperature testings of two to three fracture specimens of each material. Additional load data, which were obtained through the bottom load transducer, were used to check the accuracy of the finite element modeling of the load train. A KRAKf gauge at the remaining ligament of the prenotched bar was used to check the master curve which related the crack extension history with the COD data at room temperature. Details of this validation analysis are described in Ref. 57. 

All documentation furnished by the supplier should be available. User manuals, as-built drawings, instrument calibration records, and procedures for operation and maintenance (including calibration schedules) of the system should all be checked to verify that they are suitable. Supplier documentation should be reviewed for accuracy in its specifications of the various versions of software used and approved as fit for purpose. It is recommended that checks are made to verify that contingency plans, SOPs, and any Service Level Agreements (SLAs) are also in place. Any specific competencies supposed to be acquired before the IQ/OQ/PQ through training should also have been achieved — these records should be checked. 

A check on the accuracy of the numerical integrations of the atomic properties is provided by the evaluation of 1,(12). This quantity, defined in eqn (5.50), is proportional to the integral of the Laplacian of the charge density over the basin of the atom or, equivalently, to the flux in the gradient vector field of p through the surface of the atom,... 

Determination of Cd, Pb and U were performed by magnetic sector high resolution ICP-MS. The lack of CRMs in a snow matrix did not allow for a direct check of the measurement accuracy, but reasonable confidence in the reliability of data was reached through the use of other analytical techniques, i.e., ETA AAS and DP-ASV. Mean concentrations were found to be (pg g ) 0.39 for Cd, 5.0 for Pb and 0.04 for U. 

In quantitative metal analysis, high purity metals are the best for preparing standards. The use of pure metals instead of compound removes stoichiometry as a factor that needs to be included in calculating the true concentration of the standard solution. These factors are difficult to establish with extreme accuracy for most compounds because of factors such as the stability, number of water molecules, dryness, contamination and reactivity which must taken into account before use. However, if pure metals are not available, metal compounds are used which are usually checked carefully against certified standards. Many metal standard solutions of various concentrations are available through commercial suppliers in solution form but can be very expensive. The common concentration supplied is l.OgL-1 to lO.OgL-1 (or l.Omgml-1, lO.Omgml-1). These values are usually quoted as ppm for convenience and used widely in most laboratories. Commercial standards are normally checked by other methods (e.g. nuclear activation, titration, etc.) and supplied with a Certificate of Analysis to meet most accreditation requirements. Other special concentrations are also available or especially prepared on request and they are also supplied with a Certificate of Analysis. 

Through repetition of the same experiment and subsequent evaluation of the equilibrium data, the accuracy may be increased by averaging the values, if no systematic errors occur. Too high a deviation between equivalent measurements indicates problems in either the data evaluation or the experiment itself. In the latter case, it should be checked if the pumps deliver a constant flow rate and that the temperature is constant in the range of a few tenths of one centigrade. If the eluent consists of a fluid mixture, the influence of slight changes in eluent composition must be taken into account (Section 6.5.7.1). 

In the volumetric metering approach, the quantities are determined through the pumps used to send them to the mixing lines. Densities of all raw materials must be known under the particular conditions of temperature and formulation, and the accuracy of the pumping rate regularly checked to get the right mass flow rate from the volumetric flow rates. 

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