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THOMPSON, MICHAEL | Cambridge [REINO UNIDO] : Royal Society of Chemistry | AMC Technical Brief | 2005“What accuracy do you need?” This is a sensible question, which needs to be asked, yet how often do we receive a sensible answer? The naïve customer might say “the best possible accuracy”, which is not very sensible because it implies an enormou[...]
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THOMPSON, MICHAEL | Cambridge [REINO UNIDO] : Royal Society of Chemistry | AMC Technical Brief | 2005EDXRF offers significant advantages for multi-element applications in the analysis of a wide range of inorganic materials for R&D, production and quality control/trouble shooting applications, despite the better detection limit levels achieved b[...]
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THOMPSON, MICHAEL | Cambridge [REINO UNIDO] : Royal Society of Chemistry | AMC Technical Brief | 2002It is fairly well known that a basic assumption of regression is that the y-values (the dependent- or response variable) are random variables while the x-values (the independent- or predictor variable) should be error-free. This model often prev[...]
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THOMPSON, MICHAEL | Cambridge [REINO UNIDO] : Royal Society of Chemistry | AMC Technical Brief | 2003Many analytical chemists find the logic of hypothesis tests and confidence intervals hard to follow. What looks like a probability statement about a true concentration is in fact an assertion about random intervals, involving data we did not obs[...]
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THOMPSON, MICHAEL | Cambridge [REINO UNIDO] : Royal Society of Chemistry | AMC Technical Brief | 2004In some proficiency tests concerned with measuring the proportion of genetically modified organism (GMO) in food the results produced are logtransformed (converted into logarithms) before zscores are calculated [1]. The transformation can be jus[...]
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THOMPSON, MICHAEL | Cambridge [REINO UNIDO] : Royal Society of Chemistry | AMC Technical Brief | 2005Examining a calibration function for linearity is an everyday task in both validating analytical methods and routine analytical operations. Linearity is an important and desirable feature of an analytical method. For example, if a calibration fu[...]
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THOMPSON, MICHAEL | Cambridge [REINO UNIDO] : Royal Society of Chemistry | AMC Technical Brief | 2003Analysts’ estimates of the uncertainty of their results are often somewhat low. How do we know? By looking at the results of interlaboratory studies such as collaborative trials and proficiency tests. These studies are designed to make explicit [...]
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THOMPSON, MICHAEL | Cambridge [REINO UNIDO] : Royal Society of Chemistry | AMC Technical Brief | 2004While a single z-score provides a valuable indication of the performance of a laboratory, a set or sequence of z-scores provides a deeper insight. Moreover, z-scores collected over time for a single analyte/test material combination provide info[...]
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THOMPSON, MICHAEL | Cambridge [REINO UNIDO] : Royal Society of Chemistry | AMC Technical Brief | 2006Histograms are the usual vehicle for representing medium sized data distributions graphically, but they suffer from several defects. The kernel density estimate is an alternative computer-intensive method, which involves smoothing the data while[...]
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THOMPSON, MICHAEL | Cambridge [REINO UNIDO] : Royal Society of Chemistry | AMC Technical Brief | 2002There is a simple graphical method for assessing and controlling repeatability precision from a moderate number of duplicated analytical results. The data are obtained from test materials (as opposed to control materials), and the chart differs [...]
documento electrónico
ELLISON, S. L. R, Autor ; THOMPSON, MICHAEL, AutorStandard additions is a calibration technique devised to eliminate rotational matrix effects in analytical measurement. Although the technique is presented in almost every textbook of analytical chemistry, its behaviour in practice is not well d[...]
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THOMPSON, MICHAEL | Cambridge [REINO UNIDO] : Royal Society of Chemistry | AMC Technical Brief | 2003Over the last two decades, considerable strides have been made in constructing a single, self-consistent, conceptual scheme for quality in chemical measurement (and, indeed, all measurement). In the course of that effort, concepts are being clar[...]
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THOMPSON, MICHAEL | Cambridge [REINO UNIDO] : Royal Society of Chemistry | AMC Technical Brief | 2005Sampling is a topic where analytical chemists have been accustomed to use words rather loosely, which is fine in conversation but can lead to confusion in written work. In particular, we tend to use the word “sample” itself incorrectly: it is co[...]
