caa a22 4500 605465843 CHVBK 20210128100304.0 cr unu---uuuuu 210128e20150801xx s 000 0 eng 10.1007/s00769-015-1141-4 doi (NATIONALLICENCE)springer-10.1007/s00769-015-1141-4 Application of bootstrap method to evaluate bimodal data: an example of food microbiology proficiency test for sulfite-reducing anaerobes [Elektronische Daten] [Marzia Mancin, Marica Toson, Maria Grimaldi, Lisa Barco, Romina Trevisan, Paola Carnieletto, Antonia Ricci] Statistical analysis has an essential role in proficiency test (PT) evaluation, especially when the distribution of results of the enumeration of microbiological bacteria is multimodal or strongly asymmetric, outliers aside. In these specific cases, the median or the robust mean of the PT results, calculated using the algorithm described in ISO 13528 Annex C, is not entirely appropriate for estimating the assigned value. A possible solution is to estimate the modes of kernel density function of data distribution and its uncertainty by using the nonparametric bootstrap technique. This method allows estimation of the sampling distribution of a statistic empirically without making assumptions about the form of the population. In the context of the PT for the enumeration of sulfite-reducing bacteria growing under anaerobic conditions organized in 2012 by QUAlity Assurance, although all participants used equivalent methods, the results showed high variability, which supported the hypothesis that two discrepant populations occurred in the test samples. When a bimodal distribution occurs, it is reasonable to suppose that at least one of the modes could be correct, but unless independent grounds for preferring one over the other are available, it is not possible to determine the assigned value and calculate the z-score. In the case of the sulfite-reducing bacteria PT, the true mode was not identified and the performance evaluation was not provided. For this reason, the PT provider (IZSVe) asked that the participants report every unusual situation for this test, should they occur during the next PTs. In this way, it may be possible to identify a plausible assigned value and its uncertainty as bootstrap mode of kernel density and standard error, respectively, and to provide the z-score as value of performance evaluation in the case of negligible uncertainty. Springer-Verlag Berlin Heidelberg, 2015 Quality assurance nationallicence Multimodal distribution nationallicence Assigned value nationallicence Mancin Marzia Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut Toson Marica Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut Grimaldi Maria Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut Barco Lisa Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut Trevisan Romina Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut Carnieletto Paola Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut Ricci Antonia Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut Accreditation and Quality Assurance Springer Berlin Heidelberg 20/4(2015-08-01), 255-266 0949-1775 20:4<255 2015 20 769 https://doi.org/10.1007/s00769-015-1141-4 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00769-015-1141-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Mancin Marzia Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut NATIONALLICENCE 700 1- Toson Marica Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut NATIONALLICENCE 700 1- Grimaldi Maria Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut NATIONALLICENCE 700 1- Barco Lisa Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut NATIONALLICENCE 700 1- Trevisan Romina Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut NATIONALLICENCE 700 1- Carnieletto Paola Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut NATIONALLICENCE 700 1- Ricci Antonia Istituto Zooprofilattico Sperimentale delle Venezie, viale dell'Università 10, 35020, Legnaro, PD, Italy aut NATIONALLICENCE 773 0- Accreditation and Quality Assurance Springer Berlin Heidelberg 20/4(2015-08-01), 255-266 0949-1775 20:4<255 2015 20 769