Tsang-Chuan Chang

Capability performance analysis for processes with multiple characteristics using accuracy and precision

Process capability indices have been widely used in the manufacturing industry to provide numerical measures for process potential and process performance. However, from the perspective of improving process quality, there is a significant amount of process information that cannot be conveyed with a single index. Therefore, a single index does not have the ability to represent distinct problems in process performance or to provide the production department with sufficient information to make improvements. Thus, we applied an accuracy index δ and a precision index γ capable of reflecting the degree of deviation from target values and the degree of variance and incorporated the quality-level concept of the six-sigma model to develop a process quality-level analysis chart capable of analyzing the process capabilities of multiple quality characteristics. In addition to being able to directly identify the quality levels for various quality characteristics, the process quality-level analysis chart also provides recommendations for improvement of all quality-level regions to serve as a reference for production departments. Mathematical programming was used to develop a statistical hypothesis testing model to assist production departments in confirming the effectiveness of implemented improvements. This was achieved through derivation of a joint confidence interval for δ and γ from Boole’s inequality. From this, we obtained the upper and lower limits of the ( 1 − α ) × 100 % for δ and γ . Finally, we also applied the proposed approach to a case study of a five-way pipe process.

Determining critical service quality from the view of performance influence

Service quality is regarded as the key factor in obtaining competitive advantage. However, service and physical products differ fundamentally, and the voice of customers is generally fuzzy and non-quantitative, often leading to errors in the measurement of service quality. Based on the view of performance influence, this study applied fuzzy linguistics in a questionnaire to gauge the satisfaction of customers towards individual service items as well as their overall satisfaction and constructed a service performance influence matrix (SPIM) to identify service items of poor quality. We also employed the SPIM to compare the performance of the target company with that of its competitors. This method enables service-oriented companies to improve their service quality performance effectively and develops strategies to prevent their occurrence. A case study involving a Taiwanese bicycle retail outlet is discussed to demonstrate the applicability of the proposed framework in practice.

Developing control charts in monitoring service quality based on the number of customer complaints

Service industry has become the primary driving force behind global economic growth. This means that ensuring service quality is an important issue. Unfortunately, the process of providing services includes a number of variables that are difficult to control. As a result, determining the means to ensure the quality of service is a popular theme of research. In the past, researchers have always used the proportion of customers with complaints to propose a service performance index for the evaluation of service quality; however, the index alone cannot guarantee timely monitoring. For this reason, based on the number of customer complaints, this study proposes a theory-based service quality control chart to assist company management in the timely monitoring of customer satisfaction to ensure that service quality is being maintained. According to the characteristics of the service industries, we divided them into those with large sample sizes and those with small sample sizes. For each type, we developed an appropriate service quality monitoring model and explained the operating procedures of the control charts to provide managers with a means to comprehensively monitor service quality.

Sputtering Process Assessment of ITO Film for Multiple Quality Characteristics With One-Sided and Two-Sided Specifications

The evolution of technology has increased the demand for convenient and user-friendly human–machine interfaces. This demand has driven the rapid development of the touch panel industry. Functioning as a conductive medium, indium tin oxide (ITO) film is a key factor in the quality of touch screens or panels. Because the sputtering process of ITO film includes both STB- and NTB-type quality characteristics, the analysis methodology proposed in the past cannot represent distinct influences or provide the production department with sufficient reference for improvements. Therefore, the purpose of this paper is to apply the bilateral index Cpm, which fully reflects process loss and yield, to develop an effective assessment model for the sputtering process with one-sided and two-sided specifications. Traditionally, Cpm can only be used to measure the capability of processes with two-sided specifications. We used the variable transformation method to develop the multi-process capability analysis chart. This chart is capable of measuring process precision and accuracy in relation to both types of quality characteristics. When process capability falls short of required standards, manufacturers can investigate the reasons according to the position of each quality characteristic on the chart. These data provide an important point of reference for proposing improvements to the sputtering process to enhance the quality of ITO film products and increase the competitive advantage and productivity of manufacturers.

An application of DMADV methodology for increasing the yield rate of surveillance cameras

Abstract Taiwan has officially been an “Aging society” since 1993, and a growing number of elderly people there cannot receive proper care from family members. Therefore, Taiwan’s “long-distance home care services” have been classified as an emerging service industry. This industry rests mainly on information and telecommunications technology to overcome the barriers of distance and, thereby, to deliver health services. Surveillance cameras constitute important transmission equipment whose function is to provide real-time monitoring services; therefore, the quality and the efficiency of the camera adopted in the long-distance home care industry are important. Some of Taiwan’s domestic products occupy dominant positions in their respective global markets, and there are also many foreign competitors that have exhibited a formidable challenge to the prominent position of these Taiwan manufacturers. The production strategy for mature manufacturers under steep competition is to increase their quality and yield rate, steps that can prevent unnecessary waste. Some research has adopted Six Sigma to improve products’ yield rates, and the results have been remarkable. In this research, the DMADV methodology will be implemented for improving the quality of surveillance cameras and for diminishing related excess costs.

A Novel Approach Based on Performance Influence for Evaluating Criteria of Service Quality

Service quality is becoming increasingly important, largely determining whether customers patronize a company. However, each customer has a particular level of demand for a service, which requires that companies provide services with diverse characteristics to satisfy the needs of customers. This shows that customer satisfaction is the overall appraisal of companies, performed by customers after experiencing the services. Thus, to improve service quality, companies first understand the influence between individual satisfaction and overall satisfaction. Based on this concept, this study employees the SERVQUAL questionnaire to gauge the satisfaction of customers toward individual service items as well as their overall satisfaction and constructed a performance influence matrix to evaluate poor service performance. We further proposed a priority improvement evaluation index to confirm critical issues affecting service quality. Our proposed approach can aid companies to improve service quality effectively. Managers can also achieve the objective of management and development by understanding evaluation index. A case study involving a long-term care institution is discussed to demonstrate the applicability of the proposed framework in practice.

The construction and application of Six Sigma quality indices

Process quality is the primary factor in facilitating product sales. In accordance with the concept of Six Sigma, numerous studies have employed process capability indices for the determination of process quality levels. Unfortunately, existing indices present only a range of quality levels rather than a specific quality level value. This paper aims to propose Six Sigma quality indices for the assessment of quality levels associated with unilateral as well as bilateral specifications. To ensure the reliability in process assessment, we employ the lower confidence limit of the indices to serve as a standard and develop a process quality analysis chart for the simultaneous evaluation of larger-the-better, smaller-the-better and nominal-the-best quality characteristics with the aim of identifying the causes of sub-standard quality. The resulting chart also provides a valuable reference by which to guide efforts aimed at improvement. Finally, we present three cases and numerical experiments to demonstrate the practical applicability of the proposed method.

Process Quality Assessment Model of Hand Tools: A Case Study on the Handle of Ratchet Torque Wrench

The growing popularity of do-it-yourself (DIY) projects has increased the penetration of hand tools devices into the market. This paper thus conducts a case study on ratchet torque wrenches and develops an assessment and verification model of process quality as a means of assisting hand tool manufacturers in managing the quality of ratchet torque wrench products and promoting the on-going development in the hand tool industry. We first propose the process quality index (PQI) that can directly determine a precise level of quality based on the relationship between various process capability indices and Six Sigma quality levels. Using inference, we further develop a testing model of PQI to evaluate the quality level reached of process performance. The present case study is investigated to illustrate the practical applicability of the proposed method. We believe that the proposed model will facilitate the production of high-value products and thereby enhance the competitive advantage of firms in Taiwan.

A novel approach to deriving the lower confidence limit of indices Cpu, Cpl, and Cpk in assessing process capability

Process capability indices (PCIs) are widely used as a measure of process potential and process performance. Unfortunately, the use of sample data to estimate PCIs means that any error in the sampling can introduce considerable uncertainty into the assessment of process capability. This necessitates the use of the lower confidence limit (LCL) in the estimation of minimum process capability. Furthermore, the complexity of sampling distributions of the PCIs greatly hinders interval estimation, such that only an approximate or asymptotic LCL can be achieved. This paper proposes a novel approach to deriving the LCL of indices Cpu, Cpl and Cpk using Boole’s inequality and DeMorgan’s theorem. This approach is based on subsample data collected from a stable process. Hypothesis testing is also used to determine whether the process is capable of satisfying the quality requirements of customers. We calculated the critical values of the PCIs for various significance levels, capability requirements and sample sizes. Finally, we present analysis of two cases to demonstrate the applicability of the proposed approach.

Evaluating the Performance of Physical Fitness by Statistical Inference of Physical Fitness Index

Improving fitness levels is a key area of preventive medicine and plays an essential role in health promotion. Most organizations, constrained by time, manpower, and cost, conduct fitness tests on a random sample of the population in order to gain an understanding of overall fitness levels. However, a great degree of uncertainty may be introduced into performance assessments owing to sampling errors. Therefore, it is important to take sampling errors into account. For this reason, this article proposes a physical fitness index (PFI) based on 5 components: (1) cardiorespiratory endurance, (2) muscular endurance, (3) muscular strength, (4) flexibility, and (5body composition. Using statistical inference, we further develop a testing model of PFI to evaluate the performance of physical fitness. We hope that the results of our research contribute to the accurate determination of the overall fitness levels of the population and help provide a valuable reference for improving fitness levels. Finally, we present an example to illustrate the applicability of the proposed PFI in practice.