Evaluation of Analytical Data: A Practical Guide for Geoanalysts

Lister, Bob

doi:10.1111/j.1751-908x.1982.tb00353.x

Cited by 59 publications

(18 citation statements)

References 8 publications

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“…In reviewing individual data sets during 1994 a consistent observation was the non-normal skewed data sets found for soil extractable nutrients independent of soil. These observations are consistent with those in the geoscience field (8).…”

Section: Resultssupporting

confidence: 93%

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A proficiency testing program for the agricultural laboratory industry results of the 1994 program

Miller

Kotuby‐Amacher

Dellavalle³

1996

Communications in Soil Science and Plant Analysis

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The accuracy of soil and plant analytical results are occasionally called into question by laboratory clientele. Although laboratories generally conduct internal quality assurance procedures, there are few external performance testing programs for the industry. In the spring of 1994, a proficiency testing program was initiated for soil and plant samples for agricultural laboratories in the Western United States to provide an external quality control for the laboratory industry. The program involves the quarterly exchange of soil and plant samples on which soil salinity, soil fertility, and plant nutrition analyses are conducted. For the 1994 program, 103 laboratories from 23 states and Canadian provinces participated. Overall, soil salinity and pH analyses were highly reproducible across soils and laboratories through the year. Variability in soil nitrate results were lower than noted in past interlaboratory exchanges independent of soil sample. Results for extractable soil bicarbonate phosphorus were variable independent of soil and indicate a significantly positive skewed distribution. Plant nitrogen (N) and phosphorus (P) results were consistent across samples, laboratories, and methods. Variability in plant nitrate increased with decreasing tissue concentrations. Overall accuracy and precision of reported results, based on the use of a NIST certified reference botancial sample, were excellent for N, P, potassium (K), calcium (Ca), and copper (Cu). Generally for any given analysis the results of approximately 10% 451

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Section: Resultssupporting

confidence: 93%

“…Outlier or extreme values are identified using the ratio of extreme value technique developed by Dixon and Massey (2). Similar techniques have been described in the geoscience field (8). The technique is based on a ratio between a single reported value and the range of all reported values.…”

Section: Introductionmentioning

confidence: 99%

A proficiency testing program for the agricultural laboratory industry results of the 1994 program

Miller

Kotuby‐Amacher

Dellavalle³

1996

Communications in Soil Science and Plant Analysis

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“…An underlying assumption of the linear regression model is normality: In this case if the radionuclide distribution deviated significantly from normal, the nonparametric Spearman rank correlation coefficient ( r , ) was used and was tested at an a = 0.05 (Shaw and Wheeler 1985). The normality of the distribution was tested using two statistics, the onesample Kolmogorov-Smirnov test, using an a = 0.15 to reduce the probability of a Type I1 error (Stephens 1974;Rao et al 1979) and the skewness factor with an a = 0.05 (Lister 1982).…”

Section: Discussionmentioning

confidence: 99%

Statistical Analysis of Gamma-emitting Radionuclide Concentrations for Three Fields in Southern Saskatchewan, Canada

Sutherland¹,

Jong²

1990

Health Physics

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During 1988, the spatial variability of the natural gamma-emitting radionuclides (238U, 232Th, and 40K) and the artificial radionuclide 137Cs were studied in three near-level unfertilized fields in Saskatchewan, Canada. One field was used as a native (uneroded) control site; the other two sites have been cultivated, one since 1979 and the other since at least the 1940s. The two cultivated sites have been eroded by aeolian processes and tillage practices. Autocorrelation analysis indicated that most of the radionuclides were not serially correlated for the two depth increments sampled (0-15 cm and 15-30 cm). Autocorrelation is a necessary procedure when equally spaced transect sampling is employed, since sample independence cannot be assumed. Robust and nonrobust statistical summaries are presented for the selected gamma-emitting radionuclide concentrations. Robust statistical estimates of location and dispersion are favored when distributions are not normal or when the distribution is skewed. Median concentrations for the three fields indicated that 238U, 232Th, 40K, and 137Cs were similar to areas in the U.S. and to other areas in southern Saskatchewan. Median 238U activity concentrations were between 31.4 and 34.1 Bq kg-1; 232Th concentrations were between 29.6 and 31.2 Bq kg-1; 40K concentrations were between 471 and 502 Bq kg-1; and 137Cs concentrations were between 10.0 and 12.6 Bq kg-1. The variability of natural radionuclides in a given field for a specific depth increment was generally low, with coefficients of variation less than or equal to 10%. The variability of 137Cs concentrations was greater, ranging from 18% to 23%. Nonparametric tests indicated a significant decrease in 214Bi concentration (238U indicator corrected for 222Rn) with depth of the 1979 field, and an increase in 228 Ac (232Th) with depth in the 1940s field. Significant differences in concentration between fields were indicated for all radionuclides except for 228 Ac. The possible reasons for differences in depth and between fields are briefly discussed.

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“…These problems are partly related to clustering of data because of selected methods and may be considerable for some determinations (Abbey, 1991), which will affect all calibration curves based on such geostandards. Useful guides for the statistical test of data for geostandards have been presented by Lister (1982;.…”

Section: Most Chemical Rock Analyses Conducted During Ocean Drillingmentioning

confidence: 99%

Trace Element Determinations by X-Ray Fluorescence Analysis: Advantages, Limitations, and Alternatives

Boström¹,

Bach²

1995

Proceedings of the Ocean Drilling Program, 142 Scientific Results

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A statistical study of data files obtained by repeated X-ray fluorescence analyses (XRF) of many major and 13 trace components in 20 reference materials was conducted aboard JOIDES Resolution. The results indicate that XRF is excellent for determining most main elements in many rocks and of some trace elements (for instance Nb, Y, Sr and Rb) even at low concentrations (4-10 ppm) and that XRF data obtained aboard ship are of the same quality as XRF data reported from land-based laboratories.Other trace components, however, are harder to determine by XRF; thus, Ba concentrations below 20 ppm in basaltic rocks are impossible to measure with satisfactory precision under routine conditions, and determinations of Ce, V, and Zr at low levels may be of questionable quality.Additional trace element data can be obtained through alternative, more versatile methods, which will permit a significant broadening of the geochemical programs aboard JOIDES Resolution.

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Evaluation of Analytical Data: A Practical Guide for Geoanalysts

Cited by 59 publications

References 8 publications

A proficiency testing program for the agricultural laboratory industry results of the 1994 program

A proficiency testing program for the agricultural laboratory industry results of the 1994 program

Statistical Analysis of Gamma-emitting Radionuclide Concentrations for Three Fields in Southern Saskatchewan, Canada

Trace Element Determinations by X-Ray Fluorescence Analysis: Advantages, Limitations, and Alternatives

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