Proficiency testing is the regular testing of the performance of individual laboratories by an external agency. Stable and effectively homogeneous elemental solutions of different concentrations ranging were prepared at NPL and were certified by round robin test. These certified reference materials (CRMs) along with reports containing all information, where the laboratories were identified only by a reference number were being distributed to sixty seven participant laboratories. In this paper the data of lead (Pb) elemental solution of 1-5 mg/l is only presented for outlier detection. The results received from the sixty four numbers of laboratories for Pb elemental solution statistically evaluated with different approaches viz. Cochran’s test, Grubb’s test, Hampel’s test, classical z-score, median and NIQR method, robust statistical analysis : Algorithm A (ISO 13528) and NATA method. The robust estimate of average and uncertainty values derived from ISO 13528 method are very close to the reference value for the 1 and 2 mg/l of Pb elemental solutions. The performance of the laboratories was expressed by z-score and the laboratories having z< 2 are classified as satisfactory, 2 < z < 3 are classified as questionable and z> 3 are considered as unsatisfactory. Among all the methods, the highest number of outlier i.e. about 30 % obtained by NATA statistical analysis. As NATA method considers variance in both within and between laboratory results so it seems to be the most suitable method for outlier detection for the present data set evaluated in this study.
| Published in | American Journal of Theoretical and Applied Statistics (Volume 2, Issue 6) |
| DOI | 10.11648/j.ajtas.20130206.21 |
| Page(s) | 233-242 |
| Creative Commons |
This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited. |
| Copyright |
Copyright © The Author(s), 2013. Published by Science Publishing Group |
Proficiency Testing, Statistical Analysis, Z-Score, Outlier
| [1] | ISO/IEC 17025, General Requirements for the Competence of Testing and Calibration Laboratories, International Standards Organization (ISO), Geneva, 1999. |
| [2] | ISO/IEC 17043:2010(E) Conformity assessment-General requirements for proficiency testing. International Standards Organization, Geneva. First edition 2010-02-01. |
| [3] | ILAC-G13: Guidelines for the requirements for the competence of proficiency testing schemes, 2000. |
| [4] | New statistics for NATA’s Proficiency Testing Programs, National Association of Testing Authorities (NATA), Australia, 1996. |
| [5] | ISO 13528:2005(E) Statistical methods for use in proficiency testing by interlaboratory comparisons, International Standards Organization, Geneva. First edition 2005-09-01. |
| [6] | Nordtest project No. 1483-99; 2000:35 methedology of inter-comparison Tests and statistical analysis of test results. |
| [7] | Quality assurance and quality control in the analytical chemical laboratory: A practical approaches. Piotr Konieczka and Jacek Namiesnik. Taylor & Francis Group, 2009. |
APA Style
Sushree Swarupa Tripathy, Rajiv Kumar Saxena, Prabhat Kumar Gupta. (2013). Comparison of Statistical Methods for Outlier Detection in Proficiency Testing Data on Analysis of Lead in Aqueous Solution. American Journal of Theoretical and Applied Statistics, 2(6), 233-242. https://doi.org/10.11648/j.ajtas.20130206.21
ACS Style
Sushree Swarupa Tripathy; Rajiv Kumar Saxena; Prabhat Kumar Gupta. Comparison of Statistical Methods for Outlier Detection in Proficiency Testing Data on Analysis of Lead in Aqueous Solution. Am. J. Theor. Appl. Stat. 2013, 2(6), 233-242. doi: 10.11648/j.ajtas.20130206.21
AMA Style
Sushree Swarupa Tripathy, Rajiv Kumar Saxena, Prabhat Kumar Gupta. Comparison of Statistical Methods for Outlier Detection in Proficiency Testing Data on Analysis of Lead in Aqueous Solution. Am J Theor Appl Stat. 2013;2(6):233-242. doi: 10.11648/j.ajtas.20130206.21
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Download@article{10.11648/j.ajtas.20130206.21,
author = {Sushree Swarupa Tripathy and Rajiv Kumar Saxena and Prabhat Kumar Gupta},
title = {Comparison of Statistical Methods for Outlier Detection in Proficiency Testing Data on Analysis of Lead in Aqueous Solution},
journal = {American Journal of Theoretical and Applied Statistics},
volume = {2},
number = {6},
pages = {233-242},
doi = {10.11648/j.ajtas.20130206.21},
url = {https://doi.org/10.11648/j.ajtas.20130206.21},
eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ajtas.20130206.21},
abstract = {Proficiency testing is the regular testing of the performance of individual laboratories by an external agency. Stable and effectively homogeneous elemental solutions of different concentrations ranging were prepared at NPL and were certified by round robin test. These certified reference materials (CRMs) along with reports containing all information, where the laboratories were identified only by a reference number were being distributed to sixty seven participant laboratories. In this paper the data of lead (Pb) elemental solution of 1-5 mg/l is only presented for outlier detection. The results received from the sixty four numbers of laboratories for Pb elemental solution statistically evaluated with different approaches viz. Cochran’s test, Grubb’s test, Hampel’s test, classical z-score, median and NIQR method, robust statistical analysis : Algorithm A (ISO 13528) and NATA method. The robust estimate of average and uncertainty values derived from ISO 13528 method are very close to the reference value for the 1 and 2 mg/l of Pb elemental solutions. The performance of the laboratories was expressed by z-score and the laboratories having z 3 are considered as unsatisfactory. Among all the methods, the highest number of outlier i.e. about 30 % obtained by NATA statistical analysis. As NATA method considers variance in both within and between laboratory results so it seems to be the most suitable method for outlier detection for the present data set evaluated in this study.},
year = {2013}
}
TY - JOUR T1 - Comparison of Statistical Methods for Outlier Detection in Proficiency Testing Data on Analysis of Lead in Aqueous Solution AU - Sushree Swarupa Tripathy AU - Rajiv Kumar Saxena AU - Prabhat Kumar Gupta Y1 - 2013/12/10 PY - 2013 N1 - https://doi.org/10.11648/j.ajtas.20130206.21 DO - 10.11648/j.ajtas.20130206.21 T2 - American Journal of Theoretical and Applied Statistics JF - American Journal of Theoretical and Applied Statistics JO - American Journal of Theoretical and Applied Statistics SP - 233 EP - 242 PB - Science Publishing Group SN - 2326-9006 UR - https://doi.org/10.11648/j.ajtas.20130206.21 AB - Proficiency testing is the regular testing of the performance of individual laboratories by an external agency. Stable and effectively homogeneous elemental solutions of different concentrations ranging were prepared at NPL and were certified by round robin test. These certified reference materials (CRMs) along with reports containing all information, where the laboratories were identified only by a reference number were being distributed to sixty seven participant laboratories. In this paper the data of lead (Pb) elemental solution of 1-5 mg/l is only presented for outlier detection. The results received from the sixty four numbers of laboratories for Pb elemental solution statistically evaluated with different approaches viz. Cochran’s test, Grubb’s test, Hampel’s test, classical z-score, median and NIQR method, robust statistical analysis : Algorithm A (ISO 13528) and NATA method. The robust estimate of average and uncertainty values derived from ISO 13528 method are very close to the reference value for the 1 and 2 mg/l of Pb elemental solutions. The performance of the laboratories was expressed by z-score and the laboratories having z 3 are considered as unsatisfactory. Among all the methods, the highest number of outlier i.e. about 30 % obtained by NATA statistical analysis. As NATA method considers variance in both within and between laboratory results so it seems to be the most suitable method for outlier detection for the present data set evaluated in this study. VL - 2 IS - 6 ER -
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