Sample systematic

Note that the variance does not depend on the true value x, and the mean estimator x has the least variance. The finite sampling bias is the difference between the estimate x and the true value x, and represents the finite sampling systematic part of the generalized error... 

Perhaps the most challenging part of analyzing free energy errors in FEP or NEW calculations is the characterization of finite sampling systematic error (bias). The perturbation distributions / and g enable us to carry out the analysis of both the finite sampling systematic error (bias) and the statistical error (variance). 

In this model, the finite sampling systematic error is due to the missed sampling of the important region x < Xf. The free energy estimate given by the model is... 

By subtracting (6.18) from (6.19), we obtain the finite sampling systematic error in... 

Now consider the finite sampling systematic error. As discussed in Sect. 6.4.1, the fractional bias error in free energy is related to both the sample size and entropy difference 5e N exp(-AS/kB). With intermediates defined so that the entropy difference for each substage is the same (i.e., AS/n), the sampling length Ni required to reach a prescribed level of accuracy is the same for all stages, and satisfies... 

Thus, the trends of Br content in halite sampled systematically in profiles of salt sequences may be used as a guide to ... 

A fundamental requirement for LC-MS/MS calibration materials is that matrix effects exerted by these materials are most similar to the matrix effects exerted by actual patients sample materials. Lyophilisation, virus inactivation and other procedures applied during the industrial production of calibration and control materials, may notably impact the ionization behaviour of extracts from such samples and can result in differential matrix effects in calibrators and actual patients samples. If the internal standard peak areas found for calibration samples systematically differ from those found in patients samples, inappropriateness of the calibration materials should be suspected. However, we have previously observed that calibration materials from different commercial sources lead to inaccurate tacrolimus results in an instrument specific manner, without showing deviations in the internal standard peak area. This effect was most likely related to ionization enhancement affecting the target analyte but not the homologue internal standard (ascomycin) ionization and being restricted to calibrator samples. This resulted in systematically low tacrolimus results of clinical samples in one instrument for one specific calibrator lot [52],... 

In addition to random errors derived from samplings, systematic errors are peculiar to each particular method or system. They cannot be assessed statistically. A major effect of systematic error known as bias is a shift in the position of the mean of a set of readings relative to the original mean. 

Figure 2.4 Systematic sampling. Systematic sampling divides the site into grid cells. Soil samples are collected from within each of these units, their locations geo-referenced. A drawback may be the missing of hot spots. ...

A further quality control measure that needs to be initiated at the planning phase of the project is the use of a random numbering system when collecting the samples. Systematic sample preparation and analysis errors can more easily be identified if the samples are collected in a random number order then prepared and analysed in sequential number order (Plant, 1973). Figure 5.2 illustrates this point showing that when collecting samples in sequential number order it is more difficult to distinguish... 

However, the interference effect is stiU a very serious problem in the indirect method because sample components can change the anal3Tical signal, not only by direct influence on the reagent, but also indirectly by reaction with the analyte. Because the standard solutions are prepared and measured separately from the sample, systematic error of the analytical result can be expected in both cases unless the appropriate measures (mentioned above) are taken to eliminate interferences. 

A.3 Search for the Correct Binding Mode (267-283). Just as there are many different approaches to the global minimization problem, most, if not all, have been applied to the docking problem. These include molecular dynamics, Monte Carlo sampling, systematic... 

One can do this in two possible ways. One is to sample systematically. For instance, if one is interested is understanding in great detail how the reactivity of a planar collision... 

Unless a comparison is made with a standard, which is identical in composition to the sample, systematic errors in XRF may be large. Particle size and shape are important and determine the degree to which incident beam is absorbed or scattered. Hence, standards and samples must be powdered to the same mesh size, preferably finer than 200 mesh. Simultaneous determination of several elements is possible by XRF with automated equipment. 

Natmal sources of mercury and natural bio-geochemical processes contribute heavily to reported elevated mercury concentrations in fish and water samples collected up to 900 km downstream from local gold mining activities. Based on analysis of water, sediments, and fish samples systematically collected along a 900-km stretch of the Madeira River in 1997, it was concluded that the elevated mercury concentrations in samples were due mainly to natural sources and that the effects of mercury released from gold mining sites were localized. This needs to be verified. 

Simple random sampling Systematic sampling Routine sampling Experimental sampling... 

In the discussion of characterization techniques that were used to describe /ib-poly(e-caprolactone) samples, systematic phenomena such as yield and molecular weight dependence on the branching co-monomer s feed (BHB) as molecular weight determination in general were addressed. 

Given these observations in natural samples, systematic investigations of which processes can reset metal isotope ratios, how those processes shift isotope records, and what signs can be used to detect, and possibly correct for, the effects of diagenesis are absolutely essential. Some of the experimental and theoretical studies discussed above have yielded results that will help build a fundamental understanding of how diagenesis affects stable isotopic signatures of metals, but to... 

Avoidance of any change in the quantitative composition of the original sample (systematic errors, accuracy). 

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