Precision, estimation

Because the T-ratio is larger than T(0.05, 9, 9), which is 3.179, we conclude that the systematic errors of the analysts are significant at the 95% confidence levels. The estimated precision for a single analyst is... 

The values of x in column 4 were obtained by the Ethyl Corporation by a chemical method, for which the estimated precision is 0.02 ml of tetraethyllead fluid per gallon. Comparison of columns 4 and 5 shows agreement within these limits for all samples except B62M-3 the reason for the considerably greater discrepancy here is unknown. The precision of the x-ray work is better than was expected. (The precision is sufficiently great to warrant consideration of the difference in the x-ray absorption of the base stocks, samples AOT-1 and B62M-1.) Further-... 

Chemical shift (p.p.m.) of model compounds in H20 relative to internal 1,4-dioxane (67.86 p.p.m.). Chemical shifts for these compounds are given at pH 5.5-7.5. Estimated precision for the chemical shifts is 0.05 p.p.m.h See Refs. 82 and 83. See Ref. 20.d These assignments may have to be interchanged. See Ref. 21 numbers in the brackets below the given chemical shift values refer to those published in Ref. 86. f See Ref. 19. The chemical shift for the -anomeric carbon atom was found to be 100.6 p.p.m. and was determined from an anomeric mixture of this compound. The existence of the a-Man — Ser unit was confirmed by the l]CH value (169 Hz) obtained for this compound. See Ref. 84. 

Estimated precision in the chemical shifts is 0.05 p.p.m. The chemical shifts are given relative to external 1,4-dioxane, which was introduced into some samples only to obtain chemical shifts. Spectra obtained at 258 for — 10% solutions. Spectra of compounds were obtained at 22.5 MHz see Ref. 20. Spectra of compounds were obtained at 22.5 MHz see Ref. 24.J Spectrum obtained at 100.6 MHz see Ref. 24. Data taken from Ref. 61. Chemical shifts for GalNAc only are given. The data given in the parentheses for compounds 51 and 32 refer to the carbon count. 

Finally, the estimated precision for the determination of the concentration of hydrochloric acid is obtained using equation (2.12). 

Beyond its ability to account for what is known, the second important consideration in the selection of an appropriate molecular mechanics or quantum chemical model is its cost . It is really not possible to estimate precisely how much computer time a particular calculation will require, as many factors remain uncertain. In addition to the size of the system at hand and the choice of model (both of which can be precisely defined), there are issues the quality of the guess (which in turn relates to the experience of the user) and the inherent difBculty of the problem (some things are easier than others). It is possible, however, to provide representative examples to help distinguish applications which are practical from those which are clearly not. 

Spark source (SSMS) and thermal emission (TEMS) mass spectrometry are used to determine ppb to ppm quantities of elements in energy sources such as coal, fuel oil, and gasoline. Toxic metals—cadmium, mercury, lead, and zinc— may be determined by SSMS with an estimated precision of 5%, and metals which ionize thermally may be determined by TEMS with an estimated precision of 1% using the isotope dilution technique. An environmental study of the trace element balance from a coal-fired steam plant was done by SSMS using isotope dilution to determine the toxic metals and a general scan technique for 15 other elements using chemically determined iron as an internal standard. In addition, isotope dilution procedures for the analysis of lead in gasoline and uranium in coal and fly ash by TEMS are presented. 

The Mw is more difficult to estimate precisely. The melt viscosity results provide only an order of magnitude which is about 100,000. Since Newtonian viscosity was not observed, no refinement can be made on... 

The AOAC manual for the peer-verified methods program [16] includes a table (see Table 4) with estimated precision data as a function of analyte concentration. 

The estimate precision of a polynomial model regression coefficients rises with an increase in the number of factors, because the diameter of the sphere of factor space, within which variation limits of each factor lie, also increases. 

The following table lists the 15N chemical shifts (in ppm) for common standards. The estimated precision is better than 0.1 ppm. Nitromethane, according to Levy and Lichter,1 is the most suitable primary measurement reference, but has the disadvantage of lying in the low-field end of the spectrum. Thus, ammonia (which lies in the most upfield region) is the most suitable for routine experimental use.1-6... 

A protein (HP1075 from strain 26695) that shows remote homology to the AstE AspA family is reported in the present study. The H. pylori protein sequence shares sequence identity of 17% with the profile of the AstE AspA domain family with an E-value of 10 7 and profile coverage of 81%. Also, the H. pylori protein sequence fits on the crystal structure of aspartoacylase protein from Mcsorhizobium loti with an E-value of 10 15 (estimated precision 100%). 

The estimated precision in bond lengths obtained by a least-square refinement of a data set measured by X-ray diffraction can be 0.003 A ( 0.3 pm), for a structure with unweighted R-factor less than 3%. If the data set is collected at low temperatures (20 K or 80 K), the decrease in thermal vibration can yield even better bond distances and angles. For H atom coordinates, the precision is one or two orders of magnitude lower, since the electron density around an H atom is relatively low in these cases a neutron diffraction study (which requires very large crystals) can yield better H atom positions. 

Using the technique employed earlier in this paper we have calculated the fraction of the extracted U which is in the tetraacetato form. These results are shown in Table II. The values are not precise since small solvent-dependent frequency shifts occur relative to the spectra of the pure species which were obtained in nitrile solutions. If the data in the table are plotted, a smooth curve can be drawn through all of the points, within the estimated precision, except those from the haloform solutions. The fraction of the tetraacetato complex decreases uniformly... 

Oil Shale and Solvent-Refined Coal Liquids. Measurable amounts of the heavy elements Co, Hg, As, Zn, and Se were present in both crude shale oil and in the coproduced water from the Livermore Retort Run S-11 and the Laramie 150 T Retort Run 13. In addition, the process waters from both retorts contained significant Br (bromine) and Sb, and the water from the Laramie retort contained significant uranium (U). The data for the oil and water are presented in Tables V and VI. Independent data for several elements in the Livermore S-11 oil, water shale, and split shale can be found in Reference 10. The results for process solvent and light oil from the solvent-refined coal plant are shown in Table VII. These two liquids were generally low in trace elements, although the process solvent contained some Zn and the light oil contained measurable amounts of Zn, Br, Cr, and As. Estimated precisions for the elements shown in Tables V, VI, and VII are given in Table VIII. Independent data for a number of elements in solvent-refined coal materials can be found in Reference 11. 

Where estimated precision is not shown in this table, see Table VIII. U. S. Geological Survey Standard Basalt BCR-1. 

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