Note on the bimodal distribution of PT results
| Autor: | Peter-Th. Wilrich |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Group (mathematics)
Chemistry General Chemical Engineering 010401 analytical chemistry General Chemistry Proficiency test 01 natural sciences 0104 chemical sciences Bimodality 010309 optics Normal distribution symbols.namesake Matrix (mathematics) Distribution (mathematics) 0103 physical sciences Statistics Gaussian function symbols Applied mathematics Order (group theory) Safety Risk Reliability and Quality Instrumentation |
| Zdroj: | Accreditation and Quality Assurance. 21:381-383 |
| ISSN: | 1432-0517 0949-1775 |
| DOI: | 10.1007/s00769-016-1229-5 |
| Popis: | The practitioner’s report "Treatment of bimodality in proficiency test of pH in bioethanol matrix" by Sarmanho et al. deals with a proficiency test (PT) for the measurement of pH in bioethanol. One group of 19 participating laboratories used an electrode that contained saturated LiCl and the other one KCl. The results of the LiCl group are biased, and those of the KCl group are unbiased as compared with the assigned reference value $$y_\mathrm{{RM}}$$ , and hence, the distribution of the laboratory means is bimodal. In order to deal with this situation, Sarmanho et al. present and carry out two different methods of fitting the bimodal distribution of the laboratory means: a fit by a mixture of two normal distributions and a Gaussian kernel estimation. Since this rather advanced statistical analysis does not help to solve the practical problem, some recomendations of ISO 17043 are discussed that might be useful for the coordinator of the PT and as well for the participating laboratories. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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