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Boxplot fences in proficiency testing

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Abstract

The box and whiskers plot (boxplot) has shown to be an effective data visualization tool in proficiency testing. The boxplot provides a quick visual summary of the considered data set . All the descriptive aspects of data reported in a round of a proficiency test can be studied with this plot. Location (through median and quartiles), spread (by means of the interquartile range), shape (position of the median in the box), and possible outliers (values beyond of the fences) are simultaneously observed with the boxplot. In this paper, we propose a modification of the inner fences of the boxplot, in such a way that they are in accordance with the approach based on the z score (standard ISO 13528) and therefore useful to recognize graphically questionable and unacceptable values in proficiency testing.

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Authors and Affiliations

  1. PROASECAL SAS, Bogotá, Colombia

    Clara Morales

  2. Department of Statistics, Universidad Nacional de Colombia, Bogotá, Colombia

    Ramón Giraldo

  3. Director ProgBA–CEMIC, Buenos Aires, Argentina

    Marta Torres

Authors
  1. Clara Morales
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  2. Ramón Giraldo
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  3. Marta Torres
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Correspondence to Ramón Giraldo.

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Morales, C., Giraldo, R. & Torres, M. Boxplot fences in proficiency testing. Accred Qual Assur 26, 193–200 (2021). https://doi.org/10.1007/s00769-021-01474-8

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  • DOI: https://doi.org/10.1007/s00769-021-01474-8

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