Systematic effects

A pH/Ion-meter with a resolution of only 0.1 mV is not sufficient because the ensuing quantization noise introduces an apparent deviation of at least 0.2%, and, more important in this particular case, these systematic effects lead to a bias that is strongly dependent on small shifts in 0. (See Fig. 4.24, left side.)... 

It is an important fact, that it is understood that the result of the measurement is the best estimate of the value of the measurand, and that all components of uncertainty, including those arising from systematic effects, such as components associated with corrections and reference standards, contribute to the dispersion" (ISO 3534-1 [1993]). Therefore, uncertainty marks the limits within which a result is accurate, i.e. precise and true (Fleming et al. [1996]). 

The calculation used is the calculation of the sum of squares of the differences [5], This calculation is normally applied to situations where random variations are affecting the data, and, indeed, is the basis for many of the statistical tests that are applied to random data. However, the formalism of partitioning the sums of squares, which we have previously discussed [6] (also in [7], p. 81 in the first edition or p. 83 in the second edition), can be applied to data where the variations are due to systematic effects rather than random effects. The difference is that the usual statistical tests (t, x2> F, etc.) do not apply to variations from systematic causes because they do not follow the required statistical distributions. Therefore it is legitimate to perform the calculation, as long as we are careful how we interpret the results. 

Since the correlation coefficient is an already-existing and known statistical function, why is there a need to create a new calculation for the purpose of assessing nonlinearity First, the correlation coefficient s roots in Statistics direct the mind to the random aspects of the data that it is normally used for. In contrast, therefore, using the ratio of the sum of squares helps keep us reminded that we are dealing with a systematic effect whose magnitude we are trying to measure, rather than a random effect for which we want to ascertain statistical significance. 

Clearly, better observations (preferably with a fibre-fed spectrograph) are needed to actually constrain the extent of gravitational settling. Independent temperature indicators (photometry, excitation equilibrium of e.g. Fe i) should be checked for consistency as well. It is crucial to identify and deal with systematic effects in all aspects of the analysis. 

Note that the categories relate only to how the estimate was obtained, and not to whether the uncertainty is due to a random or a systematic effect. Type A uncertainty estimates are, by definition, expressed as a standard deviation. Type B uncertainty estimates can take a number of different forms, and may need to be converted to a standard uncertainty prior to combination with other uncertainty estimates. This is discussed later in this section. 

A run is therefore regarded as being carried out under repeatability conditions, i.e. the random measurement errors are of a magnitude that would be encountered in a short period of time. In practice the analysis of a run may occupy sufficient time for small systematic changes to occur. For example, reagents may degrade, instruments may drift, minor adjustments to instrumental settings may be called for, or the laboratory temperature may rise. However, these systematic effects are, for the purposes of IQC, subsumed into the... 

Ethanol is produced as a more environmentally benign fuel. The systematic effect of ethyl alcohol differs from that of methyl alcohol. Ethyl alcohol is rapidly oxidized in the body to carbon dioxide and water, and in contrast to methyl alcohol no cumulative effect occurs. Ethanol is also a preferred alcohol in the transportation sector compared to methanol because it is derived from agricultural products and is renewable and biologically less objectionable in the enviromnent. 

An empirically derived relationships that describes the systematic effects of different neutral salts on the solubility of proteins. Collins and Washabaugh indicate that the order of ionic species eluding from a Sephadex G-10 column corresponds to the known order of effectiveness ions in the Hofmeister series on protein solubility ... 

As noted earlier, the data in Tables 4-7 did not consider fluoride intake in breastfeeding infants, who may receive lower amounts of fluoride than shown in these tables. This is nevertheless even favourable, because it is now believed that the majority of benefit from fluoride is from its topical, rather than systematic, effects, so breastfeeding is considered to be protective against dental fluorosis [3-5]. 

Kofoed, L., Tadepalli, G., Oesterheld, J.R., Awadallah, S., and Shapiro, R. (1999) Case series clonidine has no systematic effects on PR or QTc intervals in children. / Am Acad Child Adolesc Psychiatry 38 1193-1196. 

When again a second order model was used for the data it appeared that there still was some lack of fit. Therefore models were constructed which included third order model terms. Further examination of these more complicated models however revealed that there was a much too high collinearity in these models. This means that there are systematical effects in the data which cannot be explained in a completely satisfactory manner. It was decided to use the second order model and to neglect further model complexities. The model validation results of the second order model can be found in Table 6.5. 

These parameters are found by fitting the bond valence to experimentally observed bond lengths. It is this empirical fitting that gives the model its robustness, since the fitted parameters automatically compensate for a number of systematic effects. As an example, suppose that the true charge, q, of a cation differs from the formal charge, V, by a factor k as given by eqn (9.1) ... 

In addition to containing information about the size of the electron core, Rq therefore also includes hidden information about the formal charges on the atoms as well as other systematic effects such as tt bonding and the effects of thermal motion on the apparent bond length (Section 9.4). The only information that the user needs to know is that Rq applies to all the bonds between the same pair of ions (see also the discussion in Section 14.1.2). 

Starting with the pioneering work [52] Doppler-free two-photon laser spectroscopy was also applied for measurements of the gross structure interval in mnoninm. Experimental results [52, 53, 54, 55] are collected in Table 12.5, where the error in the first brackets is due to statistics and the second error is due to systematic effects. The highest accuracy was achieved in the latest experiment [55]... 

Any result for known, quantified systematic effects must be corrected. How this is accomplished is discussed later. If the result is to be traceable to in-... 

Systematic effects are different from random ones. They are always in one direction and always (in their purest form) of the same magnitude. Averaging... 

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