Statistical Quality Control Charts Research Articles

Monitoring the Reproduction Number and Stringency Index of Covid-19 Pandemic in Nigeria

In order to track the Covid-19 pandemic's reproduction number and stringency index in Nigeria, this research presents the implementation of control chart approaches. This will assist in monitoring these pertinent parameters and assist decision-makers in determining whether to impose stricter or less strict containment measures to stop the spread of the disease. The data for this study was sourced from the Our World In Data (OWID) website (https://www.owid.org). This database contains information about how the Covid-19 pandemic has spread globally. The data consists of the reproduction number and the stringency index of the pandemic from February 2020 to July 2022. The range chart was used to monitor the variability in these indices. The findings indicate that during the first 42 days of infection, the pandemic's reproduction number and stringency index are not within statistically significant ranges, and hence out of statistical control. This could explain the virus's quick spread as well as the nation's economy's suffering due to harsh government measures. The study concludes, therefore, that statistical quality control charts are a viable option for tracking a few key pandemic metrics. This would assist in educating interested parties about the necessity of taking the necessary actions to stop the spread of such a pandemic.

High Loading Micro-Si anode with Oxidation Controlled Carbon Nanotube Scaffolds: Towards Pouch Cell Fabrication in Industrial Level

Silicon (Si) emerges as a promising anode material for lithium-ion batteries (LiB) due to its ultrahigh theoretical capacity and cost-effectiveness. However, the large-scale fabrication of high-loading Si anodes remains rarely documented. Herein, we developed large-scale oxidation-controlled carbon nanotube (CNT) scaffolds with high electrical conductivity by regulating oxidation conditions. The oxidation-controlled CNTs are self-assembled into an interwoven network, facilitating their incorporation with micro-Si particles and a polymer binder to form a stable aqueous slurry. We investigated the feasibility of scalable electrode coating through rheological analysis, revealing the viscoelastic slurry suitable for industrial-scale shear-coating. Utilizing the bar-coating method, we fabricated a large-scale electrode (30 cm x 40 cm) and confirmed the uniformity of the electrode layer via statistical quality control charts, demonstrating scalability for industrial production. In terms of electrochemical performance, the optimized Si anode surpassed previously reported Si-based anodes, exhibiting a high areal capacity of 3.9 mAh cm−2 and exceptional capacity retention (94 %) after 50 cycles. Finally, we validated the development of the Si anode, nearing industrial-level standards with exceptional pouch cell performance. The oxidation-controlled CNT scaffolds not only enable scalable coating of electrode materials but also effectively mitigate the expansion of micro-Si particles by uniformly covering the Si surface.

Rapid assessment of surface water quality using statistical multivariate analysis approach: Oder River system case study

Many physicochemical and biological monitored parameters must be taken into consideration to fully evaluate the surface water environmental condition. However, there are situations where a simple and rapid assessment of the poor water quality situations is critically important. This work presents a universal methodology for monitoring of many parameters simultaneously and early detection out-of-control samples in a real-time mode. The approach uses multivariate statistical quality control chart based on Principal Component Analysis (PCA) model with two well-known measures of abnormal behaviour in a process or system: Hoteling's T2 statistics and Q-statistic. The proposed TQ_PCA quality index provides on-line assessment of the water sample quality, with no specific knowledge and assumptions about control limits for monitored parameters required. A water sample is assessed through the simple control chart using the PCA model established for training/reference samples. The power of the proposed index has been tested using water quality data from the Oder River, including the time of the largest ecological disaster in recent European river history. The proposed index showed excellent analysis performance for physicochemical water quality dataset from Polish stations and physicochemical and biological water quality dataset from German/Frankfurt station, confirming earlier reports. There were consecutive number of alarms reported by the statistical index, a month prior to the disaster when there were no evident changes in the individual parameters. The method presented in this study demonstrated capability of assessment of the major water quality parameters, whose changes preempt the uncommon event. The presented TQ_PCA index could be easily extended to any research involving a large dataset of monitoring parameters from any industrial chemical process.

Monitoring urea concentration at different slope angles in drip fertigation

The use of statistical process control tools in irrigation is becoming widespread as it allows for quick and effective investigation and detection of possible problems with drippers, especially when fertilizer is used in irrigation water and different slopes. Therefore, the research used statistical quality control charts to monitor urea concentration at different inclinations of the lateral line. The experiment was conducted in a protected environment at the Irrigation and Fertigation Laboratory - LIF) in the city of Cascavel, Paraná State, Brazil. It followed a randomized block design, in a 4x3 factorial arrangement, in which fertilizer concentrations were evaluated at three slope angles. Experimental plots were divided into two factors. The first is the type of water (clean water from an artesian well and water with a nitrogen fertilizer at 44% N) subdivided into four subplots, representing concentrations of urea (0, 2, 4, and 6 g L-1). The second factor was slope angle and represented the sub-plots: uphill (2%), level (0%), and downhill (2%). The results show that Shewhart's statistical control charts were sensitive in observing the change in uniformity due to the increase in fertilizer concentration. Water with fertilizer (4 gL-1) affected uniformity at all studied slope levels. The results also show that high concentrations of fertilizers change the pH of the water. The lowest urea concentrations showed the best distribution uniformity results.
 Keywords: control charts, drip irrigation, Shewhart, uniformity.

Students’ performance evaluation for secondary school in Mbulu district using mean and dispersion charts grade and fixed grading method

This article focuses on comparing the evaluation of students’ performance using the Mean and dispersion chart grade and fixed grading method. This quantitative study was conducted in Mbulu district council. The assessment of students’ performance is one of the challenges that face assessors in secondary schools. This quantitative study investigated students’ performance by comparing their performance using statistical quality control charts grade and fixed grading method. The study used secondary data collected from 240 sampled documents obtained from academic students’ progressive reports from six ordinary secondary schools in the Mbulu District. The students’ performance is analyzed by using statistical quality control charts grade and fixed grading method. The findings revealed that in the Mean and S chart grade method, a large number of students performed well than in the fixed grading method. The mean and S chart grade method was better than fixed grading in evaluating students’ performance since it lowers the cut-off point of the individual students’ performance. The finding has implications for evaluating students’ performance because secondary school teachers can use mean and S chart grades to raise individual students’ performance in each subject.

Advances in statistical quality control chart techniques and their limitations to cement industry

Advances in statistical quality control chart techniques and their limitations to cement industry

STATISTICAL QUALITY CONTROL AND ELECTRICAL CONDUCTIVITY FOR EVALUATION OF THE UNIFORMITY OF DIFFERENT DRIP FERTIGATION SOLUTIONS

Population growth has led to an intensified search for ways to increase the efficiency of agricultural production, including improvements of irrigation systems. The aim of this work was to evaluate the uniformity of different drip fertigation techniques, as well as their monitoring using electrical conductivity measurements and statistical quality control charts. For this, an experiment was performed according to a fully randomized design, with six treatments: T1) water (control); T2) Forth Frutas fertilizer; T3) Fortgreen fertilizer; T4) water (control); T5) Bio Bokashi liquid fertilizer; and T6) swine production wastewater. Each treatment consisted of 25 assays (replications). For the assays, 16 collection points were selected for measurements of volume, pH, and electrical conductivity. The data were analyzed using the Christiansen uniformity coefficient, the distribution uniformity coefficient, and the coefficient of variation of the total flow, employing Tukey’s test (5% level), together with statistical quality control charts. The results revealed uniformity above 90% for irrigation and fertigation, while statistically better control was obtained for irrigation. It could be concluded that irrigation and fertigation were similar in terms of uniformity, demonstrating the feasibility of using different fertigation solutions, while the control charts enabled efficient monitoring of the uniformity of the systems.

Application of statistical control on water quality in cisterns in the semiarid Pernambucano

In the Brazilian semi-arid region, it is necessary to use alternatives for the better use of water, since evapotranspiration rates exceed rainfall rates, which may favor salt accumulation in cistern systems. This work aimed to investigate the water quality of cisterns from communities in the semiarid region of Pernambuco state. Thus, the following physicochemical and microbiological characteristics of cistern water were monitored: color, turbidity, total dissolved solids (T.D.S.), salinity through electrical conductivity (EC), pH and total and fecal coliforms. For monitoring, statistical quality control techniques, control charts and process capacity indices were employed. Results were found with high values for microbiological, total and fecal coliforms in most samples. Control charts showed no abnormality in the process. The probable reasons for the contamination of cistern water is the lack of cleaning of the gutters that are part of the stored water catchment system. In the northeastern semi-arid population, people are looking for ways to use natural resources to ensure survival and water quality is seen as a guarantee for quality of life.

Statistical Quality Control Charts Based on Hyper-Geometrically Distributed Data

In some production and administrative processes, the occurrence of certain events is best described by a hyper-geometric distribution, which in turn should be pictorially depicted by what should be called a “hyper-geometric chart (Hg-chart)” in the field of Statistical Quality Control (SQC). However, this has never been the practice, since the existence of such a chart is absent; as such, prompting administrators and process engineers to make use of already existing charts for approximately depicting hyper-geometric processes. In this article, an SQC chart for any hyper-geometric process has been developed for the total number of events in a fixed number of units. This chart has been referred to as the Hg-chart. The center line (CC), lower control limit (LCL) and the upper control limit (UCL) have been obtained for the proposed chart with a sketch of how the proposed chart should be if used for simulation. It has been recommended that simulation should be used to test the proposed chart as this could prove to be more efficient and appropriate for describing hyper-geometric data rather than using an inappropriate chart to be an approximation for solving the problem.

Monitoring the Quantity and Period of Milk Production by a Sindhi Cow using Statistical Quality Control Charts

Monitoring the Quantity and Period of Milk Production by a Sindhi Cow using Statistical Quality Control Charts

Practical application of product and process parameters under the specified process capability value

In 2018, Chen and Chou proposed a jointly design model with manufacturing quantity, specification limits, process mean, and the parameters of X-bar control chart based on the specified process capability index Cpm or Cpmk value. This integrated model is a generalization of economic manufacturing quantity (EMQ) model with statistical quality control chart. In this study, the author presents the practical application of Chen and Chou’s model for the manufacturer. The manufacturer can apply these parameters in the design of a variable single rectifying inspection plan for the output product before shipping to the customer and the determination of the stock quantity for shipment to the customer in the newsvendor problem.

The application of quality control charts for identifying changes in time-series home energy data

Energy consumption in the home is heavily influenced by the occupants and the routines they adopt. Although these routines tend to be regarded as somewhat static in nature, more recent evidence from the social sciences suggests that patterns of consumption are actually more fluid and constantly evolve to accommodate the contingencies of everyday living. This makes detecting changes in patterns of activity and their impact on energy consumption difficult, particularly when these patterns are often invisible to the householder to begin with. Being able to identify when a change occurs, therefore, could be a powerful tool to establish the context of change and so to determine more appropriate corrective action to curb waste and create opportunities for greater flexibility in consumption. The growing adoption of smart meters and home energy monitoring provide a platform for numerical approaches, yet there is little work reported in the literature and none that have attempted to evaluate effectiveness of such methods applied to detect changes in behaviour using field monitoring data from family homes. This paper reports on the application of a Change Point Detection method based on statistical quality control charts applied to identify changes in activities a family home using typical monitoring data. The approach was found to be very effective, identifying 78% of the changes that occurred over a two-year period and hence the outlook for such methods is promising. The findings suggest that such techniques could significantly improve the quality of information provided in energy feedback and so could play a significant role in the pursuit of more efficient energy use in the home by adding value to monitoring systems and services.

The Impact of an Interventional Pulmonary Program on Nontherapeutic Lung Resections.

Pulmonary resection can concurrently diagnose and treat known or suspected lung cancer, but is not without risk. Benign resection rates range widely (9% to 40%). We evaluated the impact of an Interventional Pulmonology (IP) program and dedicated Pulmonary Nodule Clinic on surgical benign resection rates at a single institution. An IP program was initiated in August 2010 that offered advanced diagnostic techniques and a dedicated Pulmonary Nodule Clinic was opened in August 2013. We retrospectively reviewed all patients who underwent resection for known or suspected lung cancer between 2005 and 2015 at our tertiary referral hospital. Demographics, preoperative tissue diagnoses, surgical procedure, final pathology, and staging were collected. Quarterly benign resection rates were calculated and plotted on a statistical quality control chart (P-Chart) to determine the impact of the IP program and Pulmonary Nodule Clinic on benign resection rates over time. Of 1112 resections, 209 (19%) were benign. Variation in quarterly benign resection rates decreased after introduction of the IP program in 2010, and a significant (P<0.05) sustained decrease in the quarterly benign resection rate occurred after introduction of the pulmonary nodule clinic in 2013 to a new baseline of 12% compared with 24% before 2010. After introduction of the IP program, mean quarterly preoperative tissue diagnostic rates increased from 45% to 58% (P<0.01). Integration of an IP program employing advanced diagnostic bronchoscopic techniques has improved preoperative diagnostic rates of suspicious pulmonary nodules and in combination with a pulmonary nodule clinic has resulted in fewer benign resections.

A Comparative Analysis of Bootstrap Multivariate Exponentially-Weighted Moving Average (BMEWMA) Control Limits

In the manufacturing and service industries, multivariate statistical quality control charts are mostly used to determine whether a process is performing as intended or if there are some special causes resulting in the variation of an overall statistics. Normally, control charts are obtained under the assumption that the variable under study follows some form of parametric distribution. When this assumption is violated, the performance of such control chart often gives false alarm signals. To address this problem, the Multivariate Exponential Weighted Moving Average (MEWMA) control limits have been proposed in existing literature. This article focuses on reviewing this existing method with a view to developing a novel approach based on the use of bootstrap. Results from a performance study shows that the proposed method enables the setting of control limits that can enhance the easy detection of out of control signals.

Enhanced adaptive CUSUM charts for process mean

ABSTRACTA statistical quality control chart is an important tool of the statistical process control, which is widely used to control and monitor a production process. The CUSUM chart is designed to detect a specific shift, provided that the shift size is known in advance. In practice, however, shift sizes are rarely known. It is then customary to use an adaptive CUSUM chart, which can effectively detect a range of shift sizes. In this paper, we enhance the sensitivities of the improved adaptive CUSUM mean charts using an auxiliary-information-based (AIB) mean estimator. The run length performances of the proposed charts are compared with those of the AIB adaptive and non-adaptive CUSUM charts in terms of the average run length (ARL), extra quadratic loss, and integral relative ARL. These run length comparisons reveal that the proposed charts are more sensitive than the existing charts when detecting different kinds of shift in the process mean. An example is given to demonstrate the implementation of existing and proposed charts.

An adaptive approach to EWMA dispersion chart using Huber and Tukey functions

AbstractRandom causes are vital part of every process in manufacturing and nonmanufacturing environments, and these do not affect the product features. Special causes, on the other hand, come because of some burden(s) in a process and requires special attention; otherwise, it ruins the products excellence. Special causes are categorized into small, moderate, and large shifts and are handled by statistical quality control charts. The Shewhart control chart is well known for large shifts, while the cumulative sum and exponentially weighted moving average are more effective in detecting small to moderate shifts. However, in practice, many processes require the simultaneous monitoring of both the small to the large shifts. In this study, we have designed an adaptive EWMA for dispersion parameter in connection with Huber and Tukey's bisquare functions. The performance measures used in this study include average run length, extra quadratic loss, relative average run length, and performance‐comparison index. We have observed that the study proposals are good competitors to the other counter parts for an efficient monitoring of shifts of varying amounts. An illustrative example using real data is given to demonstrate the implementation of the study proposal.

Effect of Calcium Hypochlorite in Drip Irrigation System After Application of Red Potassium Chloride

The use of water in agriculture should be monitored in order to be more efficient, with irrigation being the largest consumer of water in rural areas. Small farmers who are part of family farming have few resources to develop profitable activities and aiming their well-being, have created family irrigation kits which is a small drip irrigation system. The systems durability depends of some factors like clogging risk of drippers, which is often caused by the quality of the water used or the application of fertilizers to the irrigation water. This research aimed to analyze a family irrigation system with application of red potassium chloride, followed by a chemical agent to clear drippers (calcium hypochlorite) with water application before and after the fertilizer and chemical products (four treatments). At the after, the evaluations were analyzed with statistical quality control charts where the problem was detected in the final of application of the fertilizer, and the process capacity was analyzed showing that it was capable and also was analyzed the degree of system clogging in relation to the obstruction with the fertilizer and clearing with the chemical agent, which resulted in the recovery of the irrigation system (initial flow and distribution uniformity same the final) with recommendations for the use of fertilizers by drip irrigation like open the end lines after the fertigation and dissolve the fertilizer fully before application.

Statistical quality control charts for measuring educational service quality at Albaha University, Saudi Arabia, from the viewpoint of students

تم استخدام خرائط ضبط الجودة الإحصائية لتقييم جودة الخدمة التعليمية في جامعة الباحة، ويهدف هذا البحث إلى استخدام خرائط ضبط الجودة الإحصائية لقياس مستوى الجودة وفجوة الجودة بين توقعات الطلبة وإدراكاتهم لمستوى الخدمة الذي تقدمه جامعة الباحة. حيث تم اختيار عينة من 200 طالب وطالبة عشوائيا باستخدام العشوائية العنقودية من 4 كليات خلال الفترة 01 – 30/2015م، وجمعت البيانات من خلال استبيان جودة الخدمة الذي يقيس توقعات وإدراكات الطلاب للخدمة في خمسة أبعاد للخدمة والتي تتكون من الضمان، الاستجابة، التعاطف، الموثوقية، والملموسية. استخدم في البحث المنهج التحليلي الإحصائي بالتركيز على خرائط ضبط الجودة الإحصائية (الوسط الحسابي وعملية القدرة)، وقد أظهرت نتائج هذا البحث أن مستوى الخدمة كان خارج حدود ضبط الجودة في كل الكليات، وخاصة في كليتي الآداب والعلوم بالمندق والعلوم الإدارية والمالية بفجوة سالبة، وفي كليتي الآداب والعلوم الإنسانية بالعقيق والعلوم بالعقيق على التوالي بفجوة موجبة، كما أظهرت النتائج وجود فجوة سالبة في كل من أبعاد مقياس جودة الخدمة الخمسة وأقلها وأكبرها فجوة في بعدي العناصر السلامة والملموسية على التوالي.

A comparison of car following behaviors: Effectiveness of applying statistical quality control charts to design in-vehicle forward collision warning systems

This study aims to evaluate the usability of the forward collision warning (FCW) system as adopted by the statistical quality control (SQC) chart design concepts on drivers’ car following behaviors and task performance. A total of 48 highly aggressive and 48 less aggressive drivers participated in a two (aggressive driving: high vs. low; between-subjects) by two (driving workload: high vs. low; within-subjects) by three (the FCW system: five-stages vs. X-bar vs. X-bar plus exponentially weighted moving-average (EWMA) control charts; between-subjects) mixed-factorial simulation experiment. The drivers’ behaviors, response time to divided attention (DA) tasks, as well as subjective workload and trust ratings were collected. Findings showed that drivers with the FCW’s assistance improved their car-following behaviors and that the FCWs with the SQC chart design concepts showed better results than the five-stage system. Drivers who used both SQC FCWs performed correspondingly in their car-following behaviors. However, the X-bar FCW aided drivers in responding to DA tasks much faster, and drivers felt less stressed and had more trust in using the X-bar FCW system than those who used the X-bar + EWMA FCW system.

Construction Three Charts Based on Inter Quartile Range and Comparison of Efficiency with Three Charts Based on Range

This study addresses an important application of statistics in the field of industry, which is known as statistical process control. Producing high quality products order to meet consumer fulfillment requirements had always been the main issue of the quality management. In this paper, Construction of three statistical quality control charts based on inter quartile range and compared with three quality control charts based on range to justify the efficiency and sensitively of the new charts for detecting are out of control cases.