scholarly journals Bivariate confidence probability plots as a method to test the accuracy and variability of microbiological measures

2020 ◽  
Author(s):  
Antonio Monleon-Getino ◽  
Keyword(s):  
Quantitative Methods ◽  
Confidence Probability ◽  
Future Application ◽  
Interlaboratory Studies ◽  
Logarithmic Unit ◽  
Iso 13528 ◽  
Probability Plots ◽  
General Goal ◽  
T Distribution ◽  
Iso 5725

AbstractIntroductionIn an interlaboratory calibration analysis to validate a methodology that will be proposed as a European standard for domestic laundry disinfection, tests were carried out to detect if there are different behaviors in the measurements regarding accuracies and variabilities. Interlaboratory tests using different doses of disinfectant and microorganisms were carried out. ISO 5725-2 and ISO 13528 form the basis of validations of quantitative methods, providing validation specifications for interlaboratory studies. However, a need for a simple graphical method to detect interlaboratory differences in accuracy and variability was observed.ObjectivesThe general goal of this work is to present a new exploratory methodology, graphical and easy to interpret, that can determine the accuracy and variability (precision) of a variable, and compare it to the methodology applied in ISO 5725-2 and ISO 13528.MethodsWe used confidence probability plots of the multivariate Student’s t-distribution to observe the accuracy and variability of microbiological measures carried out by different laboratories during a ring trial exercise. A function in R was built for this purpose: Miriam.analysis.ellipse(Y, factor_a, eel.plot = “ t-Student”). The different observations of accuracy and variability are represented in the ellipses. If any of the points are outside the ellipse with 95% confidence, we can assume a deviation in accuracy and / or variability.ResultsTwo examples are provided with real microbiological data (logarithmic unit reductions (LR) for Pseudomonas aeruginosa, Escherichia coli, Staphilococcus aureus, Enterococcus hirae, Candida albicans and microbial counts in water (WW)). The proposed new method allowed us to detect possible deviations in the WWMEA variable and we believe it has future application for the rapid control of microbiological measures.

Introduction to Statistical Methods for Outlier Detection and Sample Homogeneity Assessment of Reference Materials and Proficiency Test Items

2021 ◽  
Author(s):  
Yi-Ting Chen ◽  
Keyword(s):  
Data Analysis ◽  
Outlier Detection ◽  
Reference Materials ◽  
Proficiency Test ◽  
Test Items ◽  
Homogeneity Assessment ◽  
Iso 13528 ◽  
Scope Of Application ◽  
Iso 5725 ◽  
Sample Homogeneity

Due to the homogeneity of the product or sample, it will affect whether it meets the scope of application and purpose. For example, the reference materials(RM) produced by the reference material producer(RMP), and the proficiency test items selected by the proficiency testing provider(PTP), in order to ensure the reference materials or proficiency test items have consistent characteristics or comparability, they should be proved to have certain homogeneity. However, before performing homogeneity assessment, it is necessary to measure the characteristic parameters of the reference materials or proficiency test items to obtain a sufficient number of measured values for data analysis, but there may be outliers in the measured values that may affect data analysis and interpretation of the results. Therefore, this article will refer to ASTM E178-16a:2016[1], ISO 5725-2:1994[2], ISO 13528:2015[3], etc., to introduce several outlier detection and homogeneity assessment methods, supplemented by case studies. Finally, this article will remind the precautions for the use of the method, so that readers can choose the appropriate method for use in the actual analysis.

scholarly journals Sampling Rate of Polar Organic Chemical Integrative Sampler (POCIS): Influence Factors and Calibration Methods

2020 ◽  
Vol 10 (16) ◽  
pp. 5548 ◽  
Author(s):  
Liyang Wang ◽  
Ruixia Liu ◽  
Xiaoling Liu ◽  
Hongjie Gao
Keyword(s):  
Organic Pollutants ◽  
Quantitative Methods ◽  
Sampling Rate ◽  
Weighted Average ◽  
Supplementary Information ◽  
Future Application ◽  
Organic Chemical ◽  
Sampling Device ◽  
In Situ Conditions ◽  
Calibration Methods

As a passive sampling device, the polar organic chemical integrative sampler (POCIS) has the characteristics of simple operation, safety, and reliability for assessing the occurrence and risk of persistent and emerging trace organic pollutants. The POCIS, allowing for the determination of time-weighted average (TWA) concentration of polar organic chemicals, exhibits good application prospects in aquatic environments. Before deploying the device in water, the sampling rate (Rs), which is a key parameter for characterizing pollutant enrichment, should be determined and calibrated accurately. However, the Rs values strongly depend on experimental hydrodynamic conditions. This paper provides an overview of the current situation of the POCIS for environmental monitoring of organic pollutants in an aquatic system. The principle and theory of the POCIS are outlined. In particular, the effect factors such as the ambient conditions, pollutant properties, and device features on the Rs are analyzed in detail from aspects of impact dependence and mechanisms. The calibration methods of the Rs under laboratory and in situ conditions are summarized. This review offers supplementary information on comprehensive understanding of mechanism and application of the POCIS. Nevertheless, the Rs were impacted by a combined effect of solute–sorbent–membrane–solution, and the influence extent of each variable was still unclear. On this basis, the ongoing challenges are proposed for the future application of the POCIS in the actual environment, for instance, the need for this device to be improved in terms of quantitative methods for more accurate measurement of the Rs.

Experimental Designs for Interlaboratory Precision Experiments: Comparison of ISO 5725 with Draft NEN 6303

1989 ◽  
Vol 72 (1) ◽  
pp. 34-37 ◽  
Author(s):  
J Zaalberg
Keyword(s):  
Standard Deviation ◽  
Edible Oils ◽  
Collaborative Study ◽  
Experimental Designs ◽  
Interlaboratory Experiments ◽  
Interlaboratory Studies ◽  
Repeatability Standard Deviation ◽  
Level Design ◽  
Iso 5725

Abstract To determine the precision of standardized analytical methods, interlaboratory experiments are carried out in which several laboratories analyze identical samples from well homogenized batches of material. From the test results, estimates of the standard deviations under repeatability as well as under reproducibility conditions are calculated. In the present work, the experimental designs recommended in the International Standard ISO 5725 have been compared with a design proposed in the draft Netherlands Standard NEN 6303. This has been done by comparing their mathematical models as well as by applying them to the results of a recent collaborative study on the determination of heavy metals in edible oils and fats. The reproducibility standard deviation is estimated equally well with both Standards, but it appeared that the designs given in ISO 5725 can lead to serious underestimation (uniform-level design) or overestimation (split-level design) of the repeatability standard deviation. By using the design proposed in NEN 6303, these biases can be avoided. Hence, it is recommended that interlaboratory studies be organized according to the design of NEN 6303.

scholarly journals Data inter-comparisons in the context of the knowledge-gaining process: an overview

ACTA IMEKO ◽  
2018 ◽  
Vol 7 (2) ◽  
pp. 73 ◽  
Author(s):  
Franco Pavese ◽  
Abderafi Charki
Keyword(s):  
Design Of Experiment ◽  
Confidence Level ◽  
Mutual Recognition ◽  
Action Plan ◽  
Experimental Measurements ◽  
Testing Laboratories ◽  
Mutual Recognition Arrangement ◽  
Iso 13528 ◽  
Iso 5725 ◽  
Working Method

<p>This paper deals with the principle of data inter-comparisons, the object of which is to increase knowledge continuously with respect to time. Although the principle is as such nothing new to metrology and testing laboratories, which carry out experimental measurements, a degree of clarification is nonetheless called for in view of the numerous questions that arise concerning ways of implementing and utilizing it to improve knowledge capitalization.</p><p>The acquisition of knowledge relative to any measurand involves a series of steps: studying the state of knowledge of the measurand, choosing a working method (typically, by establishing a design of experiment), obtaining the measurements, and analyzing them. Following this, an action plan is established in order to reduce (or if possible avoid) weaknesses or over sensitivity.</p>Comparisons are already conducted using various approaches within a laboratory. It is therefore important to understand that to assess the accuracy of a method and validate it, it is necessary to compare the results obtained by several laboratories for a given method and measurand with the correct type of inter-comparison. It is this comparison between several laboratories that, when using different methods, produces the most up to date knowledge with the highest confidence level. This paper goes over the steps that allow developing knowledge, presenting the aims and characteristics of the various inter-laboratory comparison methods, notably referring to the tools established by documents such as the BIPM MRA (the Mutual Recognition Arrangement), the ISO 5725 and the ISO 13528.

scholarly journals PROLAB SOFTWARE FOR DATA EVALUATION OF INTERLABORATORY STUDIES

2017 ◽  
Vol 44 (3) ◽  
pp. 23 ◽  
Author(s):  
Jelena M Bebić ◽  
Luka S Gažević ◽  
Christian Bläul
Keyword(s):  
Software Package ◽  
Certified Reference Materials ◽  
Precious Metals ◽  
Large Data ◽  
International Standards ◽  
Interlaboratory Comparisons ◽  
Data Set ◽  
Interlaboratory Studies ◽  
Iso 13528 ◽  
The Republic

Interlaboratory studies represent a form of external quality control for laboratories. International standards that are used for interlaboratory comparisons, ISO 17043, ISO 13528, ISO 5725, define ways of organisation of comparisons and data treatment of participating laboratories’ results. Intercomparison results can be exploited, apart from the main goal for laboratory performance evaluation, also for method validation and production of Certified Reference Materials. PROLab is a comprehensive, globaly accepted and standardized software package for evaluating interlaboratory studies. It provides large data set structures, graphical andcomputational methods for optimal use of the data. Directorate of Measures and Precious Metals has purchased and installed software package PROLab Plus, licenced as the only one in the Republic of Serbia. As such, it will be available to all interested organisers of interlaboratory comparisons, in our country.

scholarly journals Iterative Cochran’s C test as a multivariate method to detect higher than expected variability: a microbiological inter-laboratory ring trial as a case-study

2020 ◽  
Author(s):  
Antonio Monleon-Getino ◽  
Keyword(s):  
Quantitative Methods ◽  
High Variability ◽  
Wash Water ◽  
Multivariate Method ◽  
Ring Trial ◽  
Microbiological Parameters ◽  
Iso 13528 ◽  
Reduced Space ◽  
Logarithmic Reduction

AbstractIntroductionAn interlaboratory calibration analysis was carried out to validate a methodology for a European standard for domestic laundry disinfection, using different doses of disinfectant and microorganisms. ISO 5725-2 and ISO 13528 form the basis of interlaboratory validations of quantitative methods, but there is a need for a simple graphical method to detect differences in laboratory behavior in terms of accuracy and variability.ObjectiveA novel multivariate method based on the classical Cochran’s C test, as well as PCA and bootstrapping, which allows the inclusion of different correlated variables, was applied to identify higher variability than expected in factor (e.g. laboratories) levels, and the detection of multivariate outliers in a reduced space.MethodsThe proposed method is based on resampling, using the same sample many times but removing cases at random and performing Cochran’s C test for all the variables together in a reduced space.ResultsThe method was tested by checking 7 laboratories for high variability in different parameters (logarithmic reduction (LR), cross contamination (RI), and wash water (WW)). After applying the proposed statistical analyses, no reasons were found to reject any of the participating laboratories. Multiple applications of the method are possible and we describe a case study in which the multivariant iterative Cochran’s C test was used: variability detection with multiple microbiological parameters (with high variability) during an interlaboratory ring trial.

The Correspondence of Vocal Tract Resonance With Volumes Obtained From Magnetic Resonance Images

1992 ◽  
Vol 35 (5) ◽  
pp. 1009-1023 ◽  
Author(s):  
Christopher A. Moore
Keyword(s):  
Magnetic Resonance ◽  
Speech Production ◽  
Quantitative Methods ◽  
Vocal Tract ◽  
Magnetic Resonance Images ◽  
Future Application ◽  
Clinical Tool ◽  
Resonance Frequencies ◽  
Wide Range ◽  
Vocal Tract Resonance

The increasing availability of magnetic resonance imaging (MRI) as a research, and even clinical, tool in speech production makes possible a wide range of quantitative methods in vocal tract measurement. In these initial stages of application, it is essential that the limits of the method be identified. The present investigation was designed to apply the techniques of digital image analysis and volumetric measurement to MRls obtained for the vocal tract during production of continuant speech sounds, and to apply these measures to a well-established and thoroughly tested model of acoustic transmission (Stevens & House, 1955). The results demonstrated that, although there were several sources of relatively large error and measurement bias, the vocal tract volumes obtained from MRIs were significantly predictive of vocal tract resonance frequencies. These results are discussed with respect to limits and potential for future application of MRI to speech production research.

scholarly journals Qualitative PCR Method for Roundup Ready® Soybean: Interlaboratory Study

2011 ◽  
Vol 94 (1) ◽  
pp. 224-231 ◽  
Author(s):  
Takashi Kodama ◽  
Masaki Kasahara ◽  
Yasutaka Minegishi ◽  
Satoshi Futo ◽  
Chihiro Sawada ◽  
...  
Keyword(s):  
Internal Control ◽  
Qualitative Method ◽  
Quantitative Methods ◽  
Genetically Modified Organisms ◽  
False Negative ◽  
Interlaboratory Study ◽  
Roundup Ready ◽  
Pcr Product ◽  
Interlaboratory Studies ◽  
Sensitivity Specificity

Abstract Quantitative and qualitative methods based on PCR have been developed for genetically modified organisms (GMO). Interlaboratory studies were previously conducted for GMO quantitative methods; in this study, an interlaboratory study was conducted for a qualitative method for a GM soybean, Roundup Ready® soy (RR soy), with primer pairs designed for the quantitative method of RR soy studied previously. Fourteen laboratories in Japan participated. Each participant extracted DNA from 1.0 g each of the soy samples containing 0, 0.05, and 0.10% of RR soy, and performed PCR with primer pairs for an internal control gene (Le1) and RR soy followed by agarose gel electrophoresis. The PCR product amplified in this PCR system for Le1 was detected from all samples. The sensitivity, specificity, and false-negative and false-positive rates of the method were obtained from the results of RR soy detection. False-negative rates at the level of 0.05 and 0.10% of the RR soy samples were 6.0 and 2.3%, respectively, revealing that the LOD of the method was somewhat below 0.10%. The current study demonstrated that the qualitative method would be practical for monitoring the labeling system of GM soy in kernel lots.

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