Emerald | International Journal of Quality & Reliability Management | Table of Contents

Generalized q-Weibull model and the bathtub curve

Fri, 26 Jul 2013 00:00:00 +0100

Abstract

Purpose - To analyze mathematical aspects of the q -Weibull model and explore the influence of the parameter q.Design/methodology/approach - Analytical developments with graph illustrations and an application to a practical example.Findings - The q-Weibull distribution function is able to reproduce the bathtub shape curve for the failure rate function with a single set of parameters. Moments of the distribution are also presented.Practical implications - The generalized q -Weibull distribution unifies various possible descriptions for the failure rate function: monotonically decreasing, monotonically increasing, unimodal and U-shaped (bathtub) curves. It recovers the usual Weibull distribution as a particular case. It represents a unification of models usually found in reliability analysis. q -Weibull model has its inspiration in nonextensive statistics, used to describe complex systems with long-range interactions and/or long-term memory. This theoretical background may help the understanding of the underlying mechanisms for failure events in engineering problems.Originality/value - q-Weibull model has already been introduced in the literature, but it was not realized that it is able to reproduce a bathtub curve using a unique set of parameters. The paper brings a mapping of the parameters, showing the range of the parameters that should be used for each type of curve.

Applying the generalized autoregressive conditional heteroskedastic model to analyze and forecast the field failure data of repairable systems

literatinetwork@emeraldinsight.com (Yi-hui Liang) — Fri, 26 Jul 2013 00:00:00 +0100

Abstract

Purpose - This study proposes the GARCH model to analyze and forecast the field failure data of repairable systems.Design/methodology/approach - This study uses the GARCH model to analyze and forecast the field failure data of repairable systems.Findings - The proposed method can analyze and forecast failure data for repairable systems. Not only can this method analyze failure data volatility, it can also forecast the future failure data of repairable systems.Research limitations/implications - This study only adopts simulated data to verify the proposed method. Future research may use more other real product’s failure data to verify the proposed method.Practical implications - Advanced progress in the field of reliability prediction estimation can benefit engineers or management authorities by providing important decision support tools in which the prediction accuracy suggests financial and business outcomes as well as other outcome application results.Originality/value - The predictive power of the proposed GARCH model does not differ markedly from that of the neural networks in terms of the MAE and the RMSE for predicting failure data. However, the neural network model is a dynamic system with a nonlinear black-box structure and, thus, generates little analytical information for failure data. Conversely, the proposed GARCH model provides richer information, such as volatility, when analyzing and forecasting failure data.

A Cost of Quality Decision Support Model for Lean Manufacturing: Activity-Based Costing Application

literatinetwork@emeraldinsight.com (Amir Hossein Khataie, Akif Asil Bulgak) — Fri, 26 Jul 2013 00:00:00 +0100

Abstract

Purpose - The purpose of this article is to introduce a novel Cost of Quality (COQ) Decision Support Model (DSM), which can help management to track the effect of changing each incorporated Value Added (VA) and Non-Value Added (NVA) activities on each other’s cost as well as on the quality costs in real time.Design/methodology/approach - System Dynamics (SD) is used as the modeling tool due to its dynamic characteristic and its advantages; such as the possibility of integrating qualitative factors and defining learning loops. In order to enhance the performance of the model, Activity-Based Costing (ABC) cost structure has been integrated.Findings - Lean Manufacturing (LM) focuses on the methodologies and approaches that can help an enterprise to reduce the waste factors in its processes. Few studies have proven the capability of ABC in providing valuable cost information for LM implementation due to its activity-oriented nature. This study is another step towards showing the advantages of ABC in controlling the COQ via using a novel SD modeling methodology.Originality/value - The model can guide management to establish an LM oriented quality policy and control the incorporated costs effectively.

Detection of shift in process mean with x-bar chart for autocorrelated data

literatinetwork@emeraldinsight.com (sukhraj singh, D.R. Prajapati) — Fri, 26 Jul 2013 00:00:00 +0100

Abstract

Purpose - In this paper, the performance of the X-bar chart on the basis of Average Run Lengths (ARLs) is studied for the positively correlated data. The ARLs at various sets of parameters of the X-bar chart are computed by simulation. The performance of the chart at the various shifts in the process mean is compared with the X-bar chart suggested by Zang (2000) and residual chart proposed by Zang (1997). The optimal schemes suggested in this paper are also compared with Variable Parameters (VP) chart and Double Sampling (DS) X-bar chart suggested by Costa and Machado (2011).Design/methodology/approach - Positively correlated observations having normal distribution are generated with the help of the MATLAB software. The performance of the X-bar chart in terms of ARLs at the various shifts in the process mean is compared with the X-bar chart suggested by Zang (2000) and residual chart proposed by Zang (1997). The optimal schemes are also compared with VP X-bar chart and DS X-bar chart suggested by Costa and Machado (2011). Findings - The suggested optimal schemes of X-bar chart perform better at the various shifts in the process mean than the X-bar chart suggested by Zang (2000) and Residual chart suggested by Zang (1997). It was concluded that although the suggested schemes for X-bar chart detects shifts later than the VP and DS X-bar charts proposed by Costa and Machado (2011) but it involved very less number of parameters that are to be adjusted. So the time required for adjustment in case of optimal scheme of is very small compared to the VP and DS charts.Research limitations/implications - The optimal schemes of X-bar chart are developed for the normally distributed autocorrelated data. But this assumption may also be relaxed to design these schemes for autocorrelated data. Moreover the optimal schemes for chart can be developed for variable sample size and for variable sampling intervals. Practical implications - The correlation among the process outputs of any industry can be found and the suggested control chart parameters can be applied to that level of correlation. The design of optimal X-bar chart has very less number of parameters so it can be used at the shop floor level with ease. Moreover if the process outputs of the service sector are normally distributed, then the optimal chart can also be useful. Originality/value - Although it is the extension of previous work but it can be applied to various manufacturing industries as well as service industries where, the data is positively correlated and normally distributed.

The antecedents of consumer satisfaction and loyalty in fast food industry: a cross-national comparison between Chinese and Swiss consumers

literatinetwork@emeraldinsight.com (Reza Etemad-Sajadi, Daniela Rizzuto) — Fri, 26 Jul 2013 00:00:00 +0100

Abstract

Purpose - The purpose of this research is to investigate the degree of satisfaction and loyalty of Chinese and Swiss fast-food consumers. The aim is to compare Chinese/Swiss consumers’ perception of meal quality, service quality, price and their influence on their satisfaction and loyalty. The image of fast-food restaurants in the two countries is also compared.Design/methodology/approach - Two on-line surveys were conducted with two samples. The first one was conducted with Chinese consumers in China and the second one was conducted with Swiss consumers in Switzerland. We selected McDonald’s as it is globally a standardized and well-known fast-food chain. We adapted items of SERVQUAL in order to apply it to the fast food industry and to measure service quality. Data analysis was performed using ANOVA. As we had several latent variables, we also used partial least squares (PLS), a variance-based structural equation modeling method.Findings - Results showed that Chinese consumers have a better perception of meal quality and a more positive image of McDonald’s. As far as service quality perception is concerned, no major differences were observed. However reliability and tangibles dimensions seem to be more positively perceived in China. The degree of consumer satisfaction is very similar between the two samples. However, the degree of loyalty of Chinese consumers is higher compared to Swiss consumers. In addition, the image of McDonald’s seems to have a stronger influence on Swiss consumers’ loyalty. Finally, the level of service quality perceived seems to have less impact on the image of McDonald’s for Chinese consumers than for Swiss consumers.Research limitations/implications - First, as we selected McDonald’s, we must be careful in the generalization of our findings to all fast-food restaurants. Second, the two samples consist of students, which limit the generalizability of the findings. However, students are identified to be the current customers of fast-food restaurants and consequently possess an intuitive understanding of fast-food outlets.Practical implications - As consumers in China perceive a better quality of meal in McDonald’s, they might be willing to pay a higher price relative to their earnings. Compared to China, fast-food managers in Switzerland should work harder in order to improve their image. Fast-food managers must adapt themselves to the preferences of local consumers. However, this study also shows that not all variables are perceived differently by Swiss and Chinese consumers. This implies that some measures can be standardized in order to save costs.Originality/value - The study investigates the impact of nationality on the whole model, defined by customer perception of fast-food restaurants’ image, product/service quality, satisfaction/loyalty, and finally price fairness. As China is a major player in the global market based on its size and growth potential, it is interesting to compare the antecedents of customer satisfaction and loyalty in China, with a culturally different country such as Switzerland.

ASSESSMENT OF REWORK COST OF SELECTED BUILDING PROJECTS IN NIGERIA

Fri, 26 Jul 2013 00:00:00 +0100

Abstract

Purpose - Rework is seen as an unnecessary effort of redoing a process or activity that was incorrectly implemented the first time. It is caused due to so many factors such as architect changing design during construction, increase in client taste. The aim of this research is to assess rework cost of selected building projects with a view to improving project delivery process in NigeriaDesign/methodology/approach - Historical data for the study were obtained with respect to information regarding rework cost, variation cost and additional work cost were collected on twenty-two completed building project. This was achieved through convenience sampling method where ease of access to information regarding the projects is a major determinant.Findings - It was concluded that there is a significant relationship between rework cost and initial cost, final cost, cost overrun, initial time, final time and time overrun. It was also observed that Sub-Structure has the highest rework cost with 9.4% of the total average project followed by upper floor with 8.3% while the least on the rank is roof finishes with 4.8%.Research limitations/implications - The study was limited to historical data of 22 completed public building projects in Ondo state, NigeriaPractical implications - The results indicate that there is relationship between rework costs, variation cost and additional work cost. The result also indicates that substructure always has the highest percentage of building elements that is prone to rework with an approximate of 9.4% of the total rework cost of building elementOriginality/value - It was observed that rework cannot be totally eliminated; it was then recommended that it should be reduced to minimum in the construction industry by consulting appropriate professionals at different stages of the project at the right time.