Sampling Errors and Control of Assay Data Quality in Exploration and Mining Geology

Abzalov, Marat

doi:10.5772/14965

Cited by 15 publications

(16 citation statements)

References 18 publications

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“…where n = number of replicate analyses of the certified reference material, and is the critical value of the chisquare distribution at α = 0.05 (95% confidence level) for (n-1) degrees of freedom (ISO 1989;Abzalov 2008Abzalov , 2011. If the values satisfy the above inequality then the data are precise at the 95% confidence level.…”

Section: Reference Materialsmentioning

confidence: 99%

“…Because of the nonnormality of lithogeochemical data, the Thompson-Howarth method consistently underestimates precision (Stanley and Lawie 2007;Abzalov 2008Abzalov , 2011; to combat this problem, Stanley and Lawie (2007), and subsequently Abzalov (2008Abzalov ( , 2011, recommended using the average coefficient of variation:…”

Section: Thompson-howarth Long Methodsmentioning

confidence: 99%

“…In both the short and long methods the duplicate data (X 1 = original analysis, X 2 = duplicate analysis) are plotted in the form of the X-axis equal to (X 1 +X 2 )/2 and the Y-axis equal to |X 1 -X 2 |; these are the mean and absolute deviation, which is a proxy for the standard deviation, of the replicate analyses, respectively. The ThompsonHowarth method is discussed extensively in Thompson and Howarth (1978), Fletcher (1981), Stanley (2003b;2006), Stanley and Lawie (2007), and Abzalov (2008Abzalov ( , 2011.…”

Section: Duplicate Samples: Thompsonhowarth Plotsmentioning

confidence: 99%

“…An alternative method for testing precision is to use a chi-squared critical value (Abzalov 2008(Abzalov , 2011, whereby the standard deviation of the analytical results of a certified reference material (S w ) is compared to the standard deviation reported for the certified reference material (σ c ) using the following:…”

Section: Reference Materialsmentioning

confidence: 99%

“…This involves taking part of your sample, putting it through the instrumentation, discarding this material, then processing another part of your sample to be used for analysis. These cleaning steps are particularly important because often the largest potential source of contamination in analytical programs occurs during the early stages of sample preparation (Abzalov 2008(Abzalov , 2011.…”

Section: Introductionmentioning

confidence: 99%

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Modern Analytical Facilities 2. A Review of Quality Assurance and Quality Control (QA/QC) Procedures for Lithogeochemical Data

Piercey

2014

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SUMMARYQuality assurance and quality control (QA/QC) are critical components of modern analytical geochemistry. A properly constructed QA/QC program identifies both the source of analytical error and provides a means of establishing confidence in and assessing limitations of analytical data. A QA/QC program involves monitoring precision, accuracy, and potential contamination from sampling to analysis. Precision can be monitored via the systematic insertion of sample, pulp, and analytical duplicates, and reference materials; the resulting data are subsequently evaluated using scatterplots, statistical tests (e.g. % relative standard deviation), Thompson-Howarth plots, and the average coefficient of variation (CV avg (%)). Accuracy is determined through the submission of reference materials and monitored using statistical tests (e.g. % relative difference, ttest) and Shewart control charts. Blanks test contamination and results are monitored using Shewart control charts.

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Section: Reference Materialsmentioning

confidence: 99%