Bias uncorrected

Being in statistical control in an analytical laboratory is a state in which the results are without uncorrected bias and vary randomly with a known... 

Fig. 34 Comparisons of the potential energy curves between a 33-SS and b 33-RR model oligomers (50 silicon repeating units and hydrogen termini) with uncorrected and corrected PV terms. PV energy bias with 0.5 kcal per Si repeating unit was adopted hypothetically for demonstration purposes...

Although these corrections are easily implemented, they carry some consequences with respect to noise and SNR. Each CCD acquisition has readout noise, so two successive readouts will not be identical. Figure 8.30A and 8.30B are successive uncorrected CCD readouts with short integration time so the dark signal is negligible. Curve B is offset for clarity by —100 ADU. The bias... 

Uncorrected results would likely to yield an unacceptable bias which would hamper mutual recognition and comparability of data. Methods of correction may be applied widely to speciation analysis, as soon as these are based on commonly agreed protocols applied with techniques under control. The correction factors have to be calculated for each matrix since these may vary from matrix to matrix and for different levels of contents. The wide uncertainty of correction factors may yield a high relative uncertainty in the final results compared to uncorrected results (for which the uncertainty is merely related to the analysis alone). 

A fundamental issue for these schemes is that, for efficiency purposes, the acceptance ratio must be kept sufficiently high. At fixed stepsize, the acceptance ratio will tend to deteriorate with increasing system size [43], so smaller stepsizes are generally needed for large systems in practice. By contrast the straightforward, uncorrected discretization methods accept every step this leads to error due to numerical bias in proportion to a power of the stepsize. 

A fairly strong trend was found in the bias, indicating a minimum critical concentration of 7.2 compared wittian uncorrected value of 7. 66 g/liter. The second of these consisted of S calculations with Hansen-Roach cross sections. Again, a trend appears to exist, tois time toward higher values of keff as H/ Pu increases and Uie minimum critical concentration appears to be about 7.3, compared with an uncorrected value of 7.0 g/liter. 

The steady-state operation of the ICP source is beneficial for the correction of instrumental mass bias by standard-sample bracketing, where the raw (measured and uncorrected) isotope ratio data of a sample are referenced to the results obtained for an isotopic standard, which is preferentially analyzed before and after each sample [27, 35]. This technique is similar to the standardization method commonly used in gas source isotope ratio mass spectrometry. To account best for drifts in instrumental mass bias, which can be particularly severe for light elements such as Li and B, data collection often utilizes multiple but short analytical measurements for samples that are each bracketed by standard analyses. Switching between samples and standards can be very rapid, if long washout protocols are not required, and mass spectrometric measurements of about 5 min or less have been used to optimize the precision of Li and Mg isotope ratio measurements by MC-ICP-MS [111, 112]. 

We will refer to y(k + j) as the uncorrected prediction. In practice, the bias correction is often specified to be the difference between the latest measurement y k) and the corresponding predicted value, y k) ... 

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