Repetition, of measurement

The last two calculations of the confidence interval indicate in which range there are 95 out of 100 chances of finding an experimental LEL for this substance. The only legitimate experimental approach to the measurement of LEL is the repetition of measurements and the calculation of the average. The first two sequences show that the fluctuations in LEL in both of these cases cannot be considered to be linked to the uncertainty of measurement. There is a predictable cause, which cancels out all interest in this data. 

Sclerometer scratch and manual abrasion methods, considered impractical today because they involve tedious repetition of measurement to obtain the required mean, give values very close to Vickers hardness results. This... 

The electrical conductance of a given water solution increases with temperature. Field probes of electrical conductance are therefore temperature compensated. Conductivity values obtained in the field should be plotted against the corresponding TDI concentrations measured in the laboratory. A good linear correlation confirms the high quality of the data. Outstanding values should be suspected as erroneous and should be discussed with the laboratory staff for possible detection of errors or repetition of measurements. Conductivity measurements are of special use in the following cases ... 

Since the multitracers contain a large number of radioactive nuclides, y-ray spectrometry using a Ge detector is essential. The kind of elements traceable by the nuclides in the multitracer solution obtained from a target depends on the time elapsed after the irradiation, because radioactive nuclides of different half-lives are produced. Therefore, repetition of measurements increases the number of elements that can be traced. The data obtained are analyzed by means of a computer program and a database of radioactive nuclides. 

It is evident that amplitude optimization reduces noise significantly, by a factor of about 4-5. Garland et al. [107] proposed to decrease the amplitude by a factor of two per decade of frequencies. This avoids the necessity of repetition of measurements. The authors also proposed to use a chirp-z transform to carry out a discrete Fourier transform in the case where the number of points is V 2. ... 

These uncertainties cannot be eliminated but they should be reduced as far as possible by means of quality assurance procedures. Whereas incorrect calibration may be detected and corrected at a later stage, errors in the treatment of the samples cannot readily be detected and corrected. Furthermore, the storage of samples allows the repetition of measurements for the samples that are obviously not correct. Regular training and exercises should be conducted for the staff to maintain the experience of personnel as an important precondition for high quality work, especially under stress in emergencies. 

The simplest method to measure gas solubilities is what we will call the stoichiometric technique. It can be done either at constant pressure or with a constant volume of gas. For the constant pressure technique, a given mass of IL is brought into contact with the gas at a fixed pressure. The liquid is stirred vigorously to enhance mass transfer and to allow approach to equilibrium. The total volume of gas delivered to the system (minus the vapor space) is used to determine the solubility. If the experiments are performed at pressures sufficiently high that the ideal gas law does not apply, then accurate equations of state can be employed to convert the volume of gas into moles. For the constant volume technique, a loiown volume of gas is brought into contact with the stirred ionic liquid sample. Once equilibrium is reached, the pressure is noted, and the solubility is determined as before. The effect of temperature (and thus enthalpies and entropies) can be determined by repetition of the experiment at multiple temperatures. 

Statistical and algebraic methods, too, can be classed as either rugged or not they are rugged when algorithms are chosen that on repetition of the experiment do not get derailed by the random analytical error inherent in every measurement,i° 433 is, when similar coefficients are found for the mathematical model, and equivalent conclusions are drawn. Obviously, the choice of the fitted model plays a pivotal role. If a model is to be fitted by means of an iterative algorithm, the initial guess for the coefficients should not be too critical. In a simple calculation a combination of numbers and truncation errors might lead to a division by zero and crash the computer. If the data evaluation scheme is such that errors of this type could occur, the validation plan must make provisions to test this aspect. 

The author gives an exampie of a study concerning a mixture of ethanol, toluene and ethyl acetate. The case is presented in the form of a Scheffe plan for which choice of compound quantities are not optimised to obtain a good matrix as shown in the matrix of effects correiation there is no point repetition in the middle of the matrix, which thus exciudes the quantification of the level of error of measurement that can only be estimated by the residual standard deviation of the regression. Finaliy, the author uses flashpoints of pure substances from partial experimental data. The available data give 9 to IS C for ethanol (the author 12.8), 2 to 9°C for toluene (5.56) and -4 to -2°C for ethyl acetate. 

The sampling variance of the material determined at a certain mass and the number of repetitive analyses can be used for the calculation of a sampling constant, K, a homogeneity factor, Hg or a statistical tolerance interval (m A) which will cover at least a 95 % probability at a probability level of r - a = 0.95 to obtain the expected result in the certified range (Pauwels et al. 1994). The value of A is computed as A = k 2R-s, a multiple of Rj, where is the standard deviation of the homogeneity determination,. The value of fe 2 depends on the number of measurements, n, the proportion, P, of the total population to be covered (95 %) and the probability level i - a (0.95). These factors for two-sided tolerance limits for normal distribution fe 2 can be found in various statistical textbooks (Owen 1962). The overall standard deviation S = (s/s/n) as determined from a series of replicate samples of approximately equal masses is composed of the analytical error, R , and an error due to sample inhomogeneity, Rj. As the variances are additive, one can write (Equation 4.2) ... 

Repeatability is the closeness of the agreement between the results of successive measurements of the same measurand carried out under the same conditions of measurement . Repeatability conditions include the same measurement procedure, the same observer, the same measuring instrument, used under the same conditions, the same location, and repetition over a short period of time (ISO 3534-1 [1993]). 

In Kadanoff s [130, 131] two-dimensional block-spin model four neighbouring spins are assumed to have identical spins, either up or down, near the critical point. The block of four then acts like a single effective spin. The lattice constant of the effective new lattice is double the original lattice constant. The coherence length measured in units of the new lattice constant will hence be at half of its original measure. Repetition of this procedure allows further reduction in by factors of two, until finally one has an effective theory with = 1. At each step it is convenient to define renormalized block spins such that their magnitude is 1 instead of 4. The energy of such blocked spins is... 

If these conditions are met, curves as shown in Fig. 1.78.1 are measured. Figure 1.78.2 shows one measurement and one repetition of this measurement, and a third measurement with another product and other process data. 

Prior to von Laue, physicists had obtained information about crystal structure through chemical analysis, interfacia] angle measurements, and the determination of physical properties. There was little knowledge of the internal structure, although it was believed that crystals were built up by periodic repetition of some unit, probably an atom or molecule, and that these units were about 1 or 2 A apart. It was also suspected, but not confirmed, that X-rays were electromagnetic waves of about 1 or 2 A in wavelength. 

When the repetitive eyele of measurements ended at eight hours, two of the volunteers were no longer testable. The other two were impaired, but still able to seore above the eut-off that defined ineapacitation. By reviewing dots and lines on the poster-sized graphs maintained on the nursing area desks, one eould easily keep track of their scores and ratings. 

A later paper presented the results of a study of the mechanism of the sympathomimetic cardiovascular actions of I.H Cats and dogs anesthetized with allobarbital-urethane were used for measurements of pressure near the bifurcation of the descending aorta and of blood flow with electromagnetic probes. Intravenous Injection of I at 20 mg/kg was found to produce an immediate, sharp increase in blood pressure lasting for about 25 s and followed after a lag of about 6 s by an increase in blood flow. A slow drift downward of the peak systolic pressure followed. Repetition of the dose of I after an hour yielded responses similar to those after the first dose, but... 

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