The prospect of using Shewhart control charts in assessing the quality of ionometric measurements by the method of adding a sample to a standard

Modern methods of quantitative physical and chemical measurements should necessarily include procedures for quality control of research results. Recently, the procedure for quality control of measurements using control charts is gaining particular popularity in the practice of analytical measurements. To date, the methods of potentiometric studies operating in the territory of the Russian Federation, in most cases, do not include quality control using this control procedure. However, despite the complexity of the implementation and interpretation of its results, it is the use of control charts that allows you to control the quality of ionometric measurements. This is especially important for potentiometric determinations based on the addition method, since the instability of the slope of the electrode function and its deviation significantly contribute to the uncertainty of the measurement results. This article presents the main results of evaluating the use of the Shewhart control chart method for monitoring the repeatability and accuracy of measurement results. The measurement results have been obtained using an improved method of quantitative potentiometric determination of high concentrations (more than 1 gm/cdm) of ammonium ions by the method of adding a sample to the standard. In addition, an experimental substantiation of the fact that the value of the slope of the electrode function significantly affects the accuracy of measurements by the addition method has been presented. It has been revealed that when the angular coefficient of the electrode function is more than 62 mV/pNH4+ at (25±5)°C, deviations of the measurement results from the control standard by more than 50% are observed. It has been found that at (25±5)°С the most accurate results of quantitative determination are achieved when the angular coefficient of the electrode function is from 54 mV/pNH4+ to 62 mV/pNH4+ inclusive.

Robust Multivariate Shewhart Control Chart Based on the Stahel-Donoho Robust Estimator and Mahalanobis Distance for Multivariate Outlier Detection

While researchers and practitioners may seamlessly develop methods of detecting outliers in control charts under a univariate setup, detecting and screening outliers in multivariate control charts pose serious challenges. In this study, we propose a robust multivariate control chart based on the Stahel-Donoho robust estimator (SDRE), whilst the process parameters are estimated from phase-I. Through intensive Monte-Carlo simulation, the study presents how the estimation of parameters and presence of outliers affect the efficacy of the Hotelling T2 chart, and then how the proposed outlier detector brings the chart back to normalcy by restoring its efficacy and sensitivity. Run-length properties are used as the performance measures. The run length properties establish the superiority of the proposed scheme over the default multivariate Shewhart control charting scheme. The applicability of the study includes but is not limited to manufacturing and health industries. The study concludes with a real-life application of the proposed chart on a dataset extracted from the manufacturing process of carbon fiber tubes.

Estimation of production consistency of diphtheria, tetanus, and pertussis components of the DTP vaccine using Shewhart charts

The Russian Federation puts special emphasis on vaccination-related issues, in accordance with the WHO recommendations. The fact that vaccination, in particular with the diphtheria, tetanus, and pertussis vaccine (DTP vaccine), covers large population groups, accounts for the relevance of research aimed at improving the quality of vaccines. One of the ways to produce vaccines of assured quality is to maintain consistent manufacturing processes that ensure consistency of product characteristics. The stability of the technological processes may be assessed using Shewhart charts. The aim of the study was to assess the production consistency of diphtheria, tetanus, and pertussis components of DTP vaccine using Shewhart control charts. Materials and methods: the study used data from 60 batch summary protocols of a Russian-produced DTP vaccine that were submitted to the Testing Centre of the Scientific Centre for Expert Evaluation of Medicinal Products from September 2017 until April 2020. The study assessed one of the main vaccine quality characteristics—specific (protective) activity of diphtheria, tetanus, and pertussis components. Shewhart charts for the diphtheria and tetanus components were constructed based on the manufacturer’s summary protocols, while Shewhart charts for the pertussis component were constructed based on both summary protocols and the results obtained by the Testing Centre during certification of the product batches. The Shewhart charts were used in accordance with the national standards GOST R 50779.42-99 and GOST R ISO 7870-2-2015. Results: a retrospective analysis of R- and X-charts covering a 2.5-year period revealed some characteristic trends in special-cause criteria. The most alarming situation was observed for the production of the diphtheria component. The technological processes were somewhat safer in the case of the tetanus and pertussis components. The production process lacked due statistical control, which is confirmed by the lack of correlation between the results of the pertussis component activity assessment obtained by the manufacturer and the Testing Centre. Conclusions: during the analysed period, the production of the diphtheria, tetanus, and pertussis components of the DTP vaccine was not always consistent. This highlights the need to conduct research aimed at standardisation of both production processes and control test conditions.

Statistical quality control to emission uniformity in micro sprinkler with autonomous photovoltaic pumping

This work aimed to evaluate a microsprinkler irrigation system using photovoltaic energy without energy storage. The influence of photovoltaic pumping on irrigation was evaluated from the Emission Uniformity, Shewhart control charts and Process Capacity. The experiment consisted of two amorphous photovoltaic panels connected in parallel, directly connected to a water pump, where the flow of the pumping system was carried out through a ½” tube (main line), to the irrigation system composed of four microsprinklers. The voltage and current parameters were collected, and the power of the photovoltaic system was calculated, while for the irrigation system the pressures of the four microsprinklers were measured to later calculate the flow rate of the irrigation system. The experiment was conducted at the State University of Western Paraná, UNIOESTE, where 25 days of collection were carried out, in the open, at four different times, from 10:00 am to 11:00 am, from 11:05 am to 12:05 pm, from 2:00 pm to 3:00 pm and from 3:05 pm to 4:05 pm . Power generation presented a low coefficient of variation throughout the day, which resulted in flow and pressure stability, culminating in an Emission Uniformity (UE) value qualified as excellent (93.66%) according to the ASAE. The values of energy generation, flow, pressure, and emission uniformity presented a Process Capacity (CP) value above 1.33, defining the process as capable and adequate throughout the analyzed period.

Early multidrug treatment of SARS-CoV-2 (COVID-19) and decreased case fatality rates in Honduras

INTRODUCTION: Within 2 months of first detection of SARS-CoV-2 in Honduras, its government promoted nationwide implementation of multi-drug COVID-19 inpatient and outpatient treatment protocols. This was associated with a case fatality rate decrease from 9.33% to 2.97%. No decrease was seen in Mexico, a similar Latin American country that did not introduce multi-drug treatment protocols at that time. OBJECTIVE: The primary objective of the study was to use statistical process control to assess the likelihood that the decrease in case fatality rate in Honduras was due to chance, using Mexico as a control country. METHODS: Fourteen day running average COVID-19 case fatality rates in Honduras and Mexico were used to create Shewhart control charts during the first 6 months of the epidemic. The date of implementation in Honduras of the inpatient and outpatient multi-drug COVID-19 protocols were plotted on control charts, with a Mexican COVID-19 case fatality control chart for comparison. RESULTS: The case fatality rate for COVID-19 in Honduras dropped below the lower control limit 9 days after implementation of an inpatient and outpatient multi-drug therapeutic protocol, from an average 9.33% case fatality rate to 5.01%. The Honduran COVID-19 case fatality rate again dropped below the lower control limit to 2.97%, 17 days after launching a substantial government program to make the protocol medications accessible to underserved areas. Shewhart control chart plots of case fatality rates in Honduras suggest a plausible temporal association between the implementation dates of both the initial protocol implementation on May 3, 2020, and the outreach effort on June 10, 2020, and statistically significant control chart anomalies. No control chart anomalies were seen during that time in Mexico. CONCLUSION: Decreases in COVID-19 case fatality rates in Honduras were associated with both the initial publication a multi-drug COVID-19 therapeutic protocol and a subsequent outreach program.

Faktor Koreksi Diagram Kendali Shewhart pada Situasi Unconditional ARL dan Penerapannya terhadap Data Brix (Kekentalan) Saus

Statistical Proses Control (SPC) is application of method in statistics on measurements and analysis variation in proses. Shewhart control chart is ussually used as a device in SPC. In practice, the parameters prosses are usually unknown. The parameters prosses is estimated using data often from the previous processes, ARL of the control chart with estimated parameters as called as unconditional ARL. Goedhart et al propose a new correction factor to improve unconditional ARL such data unconditional ARL close to the expected ARL. In this articel we apply the correction factor of Goedhart to brix’s data of PT. XXX. We offten the obtained the upper control limit is 39.51, the lower control limit is 36.87 with mean 38.19 applying this control limit to brix’s data results that the proses is under control. Abstrak. Statistical Proses Control (SPC) merupakan penerapan metode statistik dalam pengukuran dan analisis variasi proses. Alat yang sering digunakan dalam metode SPC yaitu diagram kendali Shewhart. Dalam praktiknya, parameter proses biasanya tidak diketahui. Parameter proses tersebut biasanya diestimasi melalui data yang diperoleh dari proses sebelumnya, ARL untuk diagram kendali dengan parameter yang diestimasi dinamakan ARL unconditional. Goedhart dkk mengusulkan faktor koreksi baru untuk meningkatkan ARL unconditional yang memiliki ekspetasi sebesar ARL yang diharapkan. Dalam artikel ini kami menerapkan faktor koreksi Goedhart terhadap data brix PT. XXX dan diperoleh batas kendali atas 39.51, batas kendali bawah 36.87 dengan rata-rata 38.19 Dari implementasi diagram kendali terhadap data kekentalan diperoleh bahwa proses terkendali.