Statistical Quality Control Techniques Research Articles

Using a Modified Quality Control Charts on Academic Grades of Tertiary Institutions Students

Quality of products or services has different meaning by different Authors. Quality of academic processes in Nigeria is measured mainly by the standard set by regulatory bodies of Educational Institutions. There are a number of factors that affects quality assurance and students’ academic performance in Nigeria. This study is on the application of statistical quality control techniques on the academic performance of students. The study was aimed to investigate the performance of both National Diploma (ND) and Higher National Diploma (HND) students of the Waziri Umaru Federal Polytechnic (WUFP) Birnin Kebbi, Nigeria, using a modified version of the Shewhart’s quality control charts. Nine (9) departments from a total of 32 departments of the institution were selected. A total of 720 student’s records of Cumulative Grade Point Averages (CGPAs) were studied. Twenty student’s records each were selected per session and per programme. The results showed that the overall performance of students of the Institution is within the average standard expected of each graduand of the Polytechnic as provided by the regulatory body, the National Board for Technical Education (NBTE).

Quality Improvement of the Forging Process Using Pareto Analysis and 8D Methodology in Automotive Manufacturing: A Case Study

A systematic approach to nonconformity management and continuous improvements are the key elements of the quality management system. The objective of this paper is to present quality improvement for a manufacturing company producing forgings through the combination of several statistical methods and quality control techniques. First, Pareto analysis was applied, followed by the 8D (eight disciplines) methodology using a structured eight-step approach to problem solving following the PDCA (plan-do-check-act) method. The aim was to identify the problem and discover the critical causes of failures in the management system that allowed the problem to occur, by modifying and combining appropriate quality management methods and tools. The paper introduces a case study considering the forging process in the production of gearboxes, where customer complaints were identified in the last year, demanding the need to eliminate failures. Using the mentioned methods, the root cause of the problem was identified and permanent corrective action was planned and implemented according to the recommendations of the 8D report, which made it possible to reduce the likelihood of a recurrence of this problem and increase customer satisfaction.

Water Quality Analysis Using Machine Learning

Abstract: Human beings are dependent on the natural resources that stands for its quality. Climatic changes and environmental impacts have always been under observation. The quality of the products is always measured before use. Water, an inevitable resource ,has got a serious significance in checking its quality due to the influence of various external factors like industrial effluents, acid rain etc. This paper provide same theology for assessing the water quality that uses statistical quality control technique and Machine Learning algorithms to scale up the classification accuracy. The classification is focused on deciding if the water is suitable for drinking purpose. The goal of this study is to develop a water quality prediction model with the help of water quality factors using Artificial Neural Network (ANN) and time-series analysis.

8D REPORT APPLICATION IN PRODUCTION PROCESS OF THE REAR SEAT

The key elements of a quality management system are a systematic approach to managing non-conformances and continuous improvement. The aim of this paper is to present quality improvement in a seat manufacturing company using statistical methods and quality control techniques. First, Pareto analysis was used to dentify the problem and reveal the critical causes in the management system. Following this, the 8D methodology was applied using a structured eight-step PDCA (Plan-Do-Check-Act) approach to problem solving. The paper presents the solution with respect to a rear seat manufacturing process where customer complaints and the need to rectify defects were identified in November 2021. Using the above methods, the root cause of the problem was identified, and permanent corrective actions were planned and implemented as recommended in the 8D report to reduce the likelihood of the problem recurring and increase customer satisfaction.

ASSESSMENT OF TUYIL PARACETAMOL PRODUCTION PROCESS: A STATISTICAL QUALITY CONTROL TECHNIQUES

This research deals with the application of statistical quality control techniques on process control of paracetamol production of Tuyil Pharmaceutical Company with the aim of estimating the control limits and investigate whether the production process is under statistical control. The data used in this research was collected on two measurable quality characteristics of content and weight of paracetamol from 2015-2018. The Mean, Range and EWMA-chart together with process capability analysis were employed for measuring the production process. The result obtained from the analysis on the content of paracetamol, it was observed that for X-bar and R-Chart one point from the observations is out of the control limits while for the EWMA chart all the observations are within control and capable of improving the production process. The analysis also reveals that on the weight of paracetamol, the Mean, Range and EWMA-chart together with process capability analysis are within control and capable of improving the process of production. it was concluded that for the weight of paracetamol is statistically stable and under control while that of the content is partially stable as one point from the observations fall outside the control limits and this could be due to a small shift in the production process which is caused by chance causes of variation such as temperature, room vibration and so on. It is recommended that the company needs to take proper caution so as to improve their production process in order to meet up with consumer’s requirement.

Constructing Bootstrap Confidence Intervals of Process Capability Indices for a Three Parameter Weibull Distribution

Statistical Quality Control (SQC) technique is used in investigating the quality improvement features in a manufacturing process. One of the important tools in SQC is the process capability indices (PCIs), for measuring and comparing the characteristics of a productionprocess to engineering specifications. This article evaluates the performance of the PCIs for a three parameter Weibull distribution which is commonly employed in almost all fields of studies, such as reliability, stability and breakage data. In this article, three different techniques of constructing bootstrap confidence intervals (BCIs) of PCIs are investigated using simulations for the three parameterWeibull distribution. The three different techniques considered are percentile bootstrap, bias-corrected percentile bootstrap and normal bootstrap techniques. By using simulation, the authors investigate the average widths of the BCI of each of the three different techniques. It is found that the average widths of the bias-corrected percentile bootstrap technique are shorter than that of the other two techniques.

Bayesian Group Chain Sampling Plan for Poisson Distribution with Gamma Prior

Acceptance sampling is a statistical quality control technique that consists of procedures for sentencing one or more incoming lots of finished products. Acceptance or rejection is based on the inspection of sampled products drawn randomly from the lot. The theory of previous acceptance sampling was built upon the assumption that the process from which the lots are produced is stable and the process fraction nonconforming is a constant. Process variability is inevitable due to random fluctuations, which may inadvertently lead to quality variation. As an alternative to traditional sampling plans, Bayesian approach can be used by considering prior information of the process. Using different combinations of design parameters, this study introduces a Bayesian group chain sampling plan (BGChSP). For the first time in group chain sampling plan, the probability of lot acceptance is derived by using Poisson distribution to estimate an average number of defectives. Gamma distribution is used as a prior distribution with Poisson distribution. Taking into account both consumer’s and producer’s risks, this research considers two quality regions namely, probabilistic quality region (PQR) and indifference quality region (IQR). By minimizing consumer’s and producer’s risks, BGChSP can be used to minimize the average number of defective products in industry.

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.

Analysis Roofing Quality Control Using Statistical Quality Control (SQC) (Case Study: XYZ Company)

Quality is a dynamic condition related to products, services, people, processes and the environment that satisfy or exceeds expectations. Quality is the main factor for consumers in choosing products. The quality of products by company determine based on certain sizes and characteristics. XYZ company is a company engaged in Baja Lembaran Lapis Seng (BJLS) which produces zinc roofing. In order to survive in competitive market, improving quality and productivity of product is must for any company. Based on production on 2019 showed that there were 49,660 defective products out of 824,574 total production meaning that there were 5.95% of defective products that exceeded the companys tolerance limit of 2%. many products that defective products that cause repeat activities and losses finished products cause harm to the company. This study reports the application of statistical quality control techniques to ensure roofing quality and to minimize the presence of defective products. the results of the analysis with the P control map show that all data on the number of defects are still in the control limit with a Cp value of 0.9410, which is low improvements the product or process so able to continue to improve the quality of its products.

Editorial

Welcome to the sixth issue of the Journal of Construction Business and Management. This issue will contribute scholarly discussion to the theoretical and methodical challenges impacting construction business management research and practice. The focus is to enhance the theoretical foundation for potential explanations to the various issues affecting construction operations towards assisting in the achievement of characteristics required for efficient construction organisations, projects, developments and resource use. The topics covered in this issue are related to corporate organisational effectiveness, quality management, maintenance performance, growth of the built environment professions, building regulations and contractor's risk attitudes. The issue contains six articles that were written by fifteen scholars based in Kenya, Malaysia, New Zealand, Nigeria and South Africa.
 The first paper by Ogbu and Olatunde evaluates the measures of corporate Organisational Effectiveness (OE) of Small and Medium-sized Enterprise (SME) contractors. The study found out that the SME contractors’ corporate OE can be measured by using corporate advantage, firm experience, certification and owner background. Also, a significant relationship was found between the OE of the firm and measures of project performance. They posit that better firm experience alone does not necessarily improve a contractor’s project performance. Paper two by Abdullahi, Bustani, Hassan and Rotimi assessed the quality management practices of Nigerian construction firms. Their study revealed that inspections and statistical quality control techniques are the most widely used quality management tools by construction firms in Nigeria. Abdullahi et al. conclude that there is a low uptake of quality management practice principles within construction organisations in Nigeria and proffered solutions to mitigate these challenges. The paper by Ajayi, Koleoso, Ajayi and Faremi evaluates the satisfaction ratings of the maintenance performance of prison facilities in South-Western Nigeria. The study revealed that prison staff were satisfied with the level of cleanliness, quality of water and control of ventilation; and partially satisfied with twenty-nine other criteria that were assessed. Ajayi et al. conclude that there is a need for continuous evaluation of prison facilities to ascertain their condition and performance levels.
 The fourth paper by Rwelamila and Manchidi examines the growth of professions as a consequence of the division of expert labour evolving to fill in knowledge gaps created by emergent social forces as other knowledge areas are rendered less relevant. The study shows how professional work negatively impacts on the delivery efficiencies in the project as a temporary organisation. Also, the study explains how boundary margins keep professions relational and how the dynamics of boundary work unfold in a territorial space in a project (meso) environment. The study by Omollo the author of the fifth paper investigates key barriers to the effective regulation of the building construction industry in Kenya. The article reveals that ineffective regulation of the construction industry was prompted by joint activities of building development contractors and the limitation of the National Construction Authority (the regulator). While building development contractors were found to be non-compliant with the building regulations, while the National Construction Authority fail to enforce the rules. Omollo concludes that regular monitoring and enhanced enforcement would promote compliance and sensitisation of contractors with applicable standards. Lastly, the paper by Taofeeq and Adeleke examines the factors affecting contractors’ risk attitudes in the Malaysian construction industry. Taofeeq and Adeleke found that the four leading factors influencing contractors risk attitude in the Malaysian construction industry are project-related, working capital, human-related factors and the external environment. The findings suggest that knowledge of these factors will help contractors’ decision-making processes in project management.
 Finally, I wish to acknowledge all authors who submitted papers for consideration, members of the JCBM Editorial Board and panel of reviewers for their support, timeous review and comments that have helped in defining and improving the quality of manuscripts published by the journal. We welcome feedback and suggestions from readers towards improving the quality of the journal and in maintaining the integrity of the findings published.
 Abimbola Windapo PhD
 Editor-in-chief

Assessing Quality Management Practice in Nigerian Construction Industry

Several adverse reports on quality performance drive the need to assess quality management practice in the Nigerian construction industry. Incidences of building failures and in extreme cases, building collapse have been attributed to poor quality management among other factors. This paper assesses the quality management practices of Nigerian construction firms intending to suggest appropriate courses of action for improving quality performance. Data were collected through questionnaires administered to management staff in 20 construction firms in Abuja, Nigeria. Findings from the study show that inspections and statistical quality control techniques are the most widely used quality management tools by construction firms in Nigeria. However, the study found that the preparation of quality management plans (QMP) and quality auditing (a measure of quality assurance in building production), is not popular among Nigerian construction firms. Inadequate planning arrangements for quality, poor communication of quality requirements and lack of awareness of the benefits of quality management were identified as the most significant issues affecting quality management practice. Therefore there is a low uptake of quality management practice principles within construction organizations in Nigeria. Hence, the need to create awareness for implementing quality management principles and concepts in its construction industry.
 Keywords: Assessment, Construction industry, Nigeria, Quality management, Quality standards

An Improved multivariate generalised likelihood ratio control chart for the monitoring of point clouds from 3D laser scanners

Statistical quality control techniques are crucial for manufacturing companies with tight tolerances but high-volume data generated from laser scanners has pushed the limits of traditional control charts. In a previous work, multivariate generalised likelihood ratio control (MGLR) chart was used to identify process shifts and locate defects on artefacts by converting 3D point cloud data to a 2D image. This paper presents a 3D MGLR control chart that retains the 3D nature of the point cloud data and uses a Fourier transform of the point errors. The average run length (ARL1) of the proposed 3D MGLR was tested using a designed experiment with ten replications and varying the number of past scans and number of Regions of Interest (ROIs). The designed experiment was repeated using three defects: incorrect surface curvature, surface scratch, and surface dent. The proposed methodology identified the dent while the prior methodology never identified it. In addition, the proposed methodology had a significantly shorter ARL1 than the prior methodology for the scratch and no significant difference in the ARL1 for the incorrect surface curvature. The proposed 3D MGLR control chart enabled the usage of 3D data without needing to convert it to a 2D image.

Statistical Quality Control Analysis of Wind Energy Potential for Power Generation in Benin

Energy has been and will continue to be the driver of economy of a nation. In sharp contrast, our country Nigeria is being faced with energy poverty. This may accrue to, in fact, over reliance on conventional energy sources such as hydro power, fuels and gas etc. So, there is need to take into consideration the renewable energy as potential alternative for power generation. This work seeks to assess the wind energy potential of Edo state using a statistical method: statistical quality control technique. The detailed knowledge of the wind characteristics at a site is very crucial to install and estimate the performance of a wind energy project. The monthly and yearly highest mean wind speeds were 3.28 and 2.91 m/s respectively. The most probable wind speed and wind speed carrying maximum energy were estimated 2.84 and 4.53 m/s in 2015. Result revealed that the wind speed are statistically in control. That is, the speeds of wind fall in between their respective upper and lower limits for 2015 - 16. The result of the study revealed that the wind energy potential of Edo state is quite low for electricity generation based on the two-year wind data analysed. It is suggested that this research area should be intensified by collecting wind speed data at various locations sufficient to define its potential for power generation.

Dripper testing: Application of statistical quality control for measurement system analysis

ABSTRACT Laboratory tests for technical evaluation or irrigation material testing involve the measurement of many variables, as well as monitoring and control of test conditions. This study, carried out in 2016, aimed at using statistical quality control techniques to evaluate results of dripper tests. Exponentially weighted moving average control charts were elaborated, besides capability indices for the measurement of the test pressure and water temperature; and study on repeatability and reproducibility (Gage RR) of flow measurement system using 10 replicates, in three work shifts (morning, afternoon and evening), with 25 emitters. Both the test pressure and water temperature remained stable, with “excellent” performance for the pressure adjustment process by integrative-derivative proportional controller. The variability between emitters was the component with highest contribution to the total variance of the flow measurements, with 96.77% of the total variance due to the variability between parts. The measurement system was classified as “acceptable” or “approved” by the Gage RR study; and non-random causes of significant variability were not identified in the routine of tests.

Effect of Inaugurating the Third Set of Locks in the Panama Canal on Vessel Size, Manoeuvring and Lockage Time

The Panama Canal (PC) has recently been in the world spotlight. In August 2014, it celebrated 100 years of uninterrupted service and, in June 2016, the expansion project for the canal was inaugurated. The final project involved building a third set of locks. Once the canal started to operate, it could be seen that the way in which vessels transited the canal remained the same. However, the dimensions of locks and their revised operating procedures have had an effect on vessel size and the manoeuvres for the larger vessels. After the first transit on 26 June 2016, it was possible to have access to data on the new lockage systems for Neopanamax ships. The thorough statistical study of these new datasets (composed of Analysis of Variance (ANOVA), multivariate regression and statistical quality control techniques) has shown the main drivers of transit time across the Cocolí and Agua Clara locks. It has also made it possible to test the learning curve of Panama Canal pilots in the newly expanded canal. The effects of pilot training on the time it takes to transit through the locks, direction of entry in each lock, the type of vessel, vessel dimensions and the use of different types of manoeuvres have been analysed. The results are used to characterise and help optimise the performance of this new and unique lock system.

통계적 품질관리도를 활용한 차별적 경찰대응전략의 평가

The purpose of this research is to evaluate the quality of Differential Police Response strategy. Although it has been approximately three years since these new police response systems were introduced, there is no research to evaluate them empirically. Using two types of statistical quality control techniques, Xbar-R control charts for variables data and P charts for attributes data, this study analyzes approximately 3,000 calls reported throughout the year 2012 to the 112 Integrated Dispatch Center in Ik-san police station. The Xbar-R control charts revealed that the police did not consistently respond to an emergency call for service (i.e., code one case) within 3 minutes. The P control chart also identified that there was a significant variation in the portion/number of defective calls where police failed to respond to non-emergency calls for service within 5 minutes. The results from this study suggest the police may need to review the target response time for code 1 and code 2 respectively.

Evaluation of Quality of Concrete Road Project based on Statistical Quality Control Techniques

Evaluation of Quality of Concrete Road Project based on Statistical Quality Control Techniques

Off-Line Quality Control in Bioproducts Processing: A Case Study in Greece

In the present article we study the production of grape molasses. Data drawn from a specified biolaboratory, are properly analyzed in order to detect factors that affect significantly the Brix value and the volatile acidity of the final product. The ground that is used for planting and a variety of grapes have been taken into account. Off-line statistical quality control techniques have been employed and the outcomes are displayed and discussed in detail.

An Assessment of the Quality of Services of Kenya Power (KP) Ltd in Restoring Supply After Unplanned Interruptions Using Statistical Quality Control

The purpose of this study was to apply statistical quality control (SQC) techniques and tools to assess the customer’s experience of quality as offered by Kenya Power Ltd. It also seeks to determine whether or not the services of the company were in statistical control. The study was designed as a descriptive survey. The population consisted of 65,830 customers within Nakuru town and its environs from which four hundred customers were sampled. The sample population was stratified so that 286 were domestic consumers while the remaining 114 were non-domestic consumers. Stratified random sampling was used. The collected data was coded and summarized in the form of tables and entered into the SPSS program. Customers’ experiences were obtained and used to draw control charts, which were analyzed. It was found that the customers’ experience of service as regards the restoration of supply after unplanned interruptions was not in statistical control for both domestic and non-domestic consumers. These results are an indictment of the qualities of service of Kenya Power. The implication for the managers of service processes at Kenya Power is that they must ensure optimal service quality in the firm. In particular, urgent steps must be taken to identify the root cause or causes of special variation that result in service invariability and instability. We strongly advocate for the intensified use of statistical quality control tools in the utility services sector and particularly at Kenya Power, as a means of monitoring the production and service quality, and enabling the firm to take timely and appropriate action to correct undesirable deviation in production quality.

Measurement System Analysis Using Repeatability and Reproducibility Techniques

To monitor and improve any manufacturing process in quality control, it is important to measure the cause of the attribute for that process. The quality of measurement data depends on the repeated measurements obtained through measurement systems which will operate at a given condition. This study uses a type of statistical quality control technique called Repeatability and Reproducibility (R&R) to determine how much of the process variation is caused by the variation of the measurement system that is being used. The two types of charts that were used for this study were the ANOVA chart and the Mean & Average chart.