International Journal of Quality & Reliability Management

GERT analysis for a dissimilar two-engine aeroplane model with CCF, human error and PM : Table of Contents

Mohamed Salah El-Sherbeny — Mon Mar 15 02:05:42 GMT 2010

Abstract:
Purpose – The main objective of this paper is to study the effect of preventive maintenance (PM) on an aeroplane model performance with graphic illustration. Design/methodology/approach – The paper deals with an aeroplane model in a different way. The two engines of the plane are considered to be “dissimilar” parallel components, say A and B, with three modes of failure: hardware error; common-cause; and human error. The system involves preventive maintenance at random times. The author assumes that the failure, repair and maintenance times are independent random variables. The failure rates, repair rate and “preventive” maintenance rate are constant for each engine. The system is analyzed by graphical evaluation and review technique (GERT). Findings – The mean time to failure, mean time to repair, the steady-state availability, busy-time and idle-time are obtained numerically and graphically. Certain important results are derived as particular cases. Originality/value – For achieving high reliability of the system, the addition of PM to the model is recommended.

Cost analysis for a deteriorating system using monotone processes with warranty : Table of Contents

Sarada Yedida, Mubashir Unnissa Munavar — Mon Mar 15 02:05:42 GMT 2010

Abstract:
Purpose – The purpose of this paper is to investigate preventive-repair warranty policies for repairable deteriorating systems using Zhang's geometric process repair model. Design/methodology/approach – The paper aims to establish the importance of preventive repair during warranty. Three cost models have been developed using the average cost rate for the system as the objective function, employing N-policy for two models therein. Findings – The models have practical applications in warranty cost analysis, as product warranty is an important factor in designing an optimal maintenance policy. Originality/value – The paper observes that product warranty has not been considered in the study of maintenance policies for repairable deteriorating systems using monotone processes. The numerical example given illustrates that a preventive repair during warranty with N-policy is preferable compared with a non-warranted product or a warranted product without preventive repair.

Six Sigma quality: a structured review and implications for future research : Table of Contents

Mohamed Gamal Aboelmaged — Mon Mar 15 02:05:42 GMT 2010

Abstract:
Purpose – This paper aims to clarify emerging aspects and trends of Six Sigma literature over 17 years, from 1992 to 2008. Design/methodology/approach – The literature on Six Sigma from 417 referred journal articles in business and management disciplines, information systems and computer science, engineering, healthcare, etc. were systematically analyzed based on a scheme that consists of four distinct dimensions: publication year and journal, major themes, research type, and application sector (i.e. manufacturing vs service). Findings – A number of key findings emerged: Six Sigma research is growing rapidly, covering various disciplines and domains with a great focus on Six Sigma tools and techniques; empirical research is dominant with more emphasis on case study approach; and the growing gap between manufacturing- and service-focused articles implies the return of Six Sigma to manufacturing as its initial base. Although a large volume of literature is available on Six Sigma, the topic is still under development and offers potential opportunities for further research and applications. Originality/value – The paper provides both academics and practitioners with a useful framework for pursuing rigorous Six Sigma research through explaining the chronological growth of Six Sigma, challenging themes of Six Sigma research, dominating research types and application areas in Six Sigma, and the major sources of Six Sigma information.

Using net present value methods to evaluate quality improvement projects : Table of Contents

Valerie G. Caryer Cook, Ahad Ali — Mon Mar 15 02:05:42 GMT 2010

Abstract:
Purpose – This paper aims to propose the use of net present value methods to derive the quality costs of quality improvement projects. The proposed methodology is then demonstrated in a case study of a quality improvement to an inspection process in an automobile assembly plant. Design/methodology/approach – The approach takes the form of application of accounting net present value methods to the cost of quality methods. Findings – Quality improvements in the manufacture of durable goods do not usually have instantaneous results in warranty cost reductions, customer satisfaction or revenue expansion. The net present value method proposed gives a more accurate accounting of the expected results of quality improvement projects by considering the temporal effects of the change and the time value of money. Research limitations/implications – The case study presented contains fictitious data to protect the confidentiality of the source. While it is useful in demonstrating the application of the net present value method, it should not be used as an indication of actual costs of plant operations. Originality/value – The paper provides a unique approach to cost of quality analysis that is particularly useful in the assessment of quality improvement projects for durable goods. While much research is focused on cost of quality methods and philosophies, only a little provides the level of detail in the actual application of the methods found in the case study.

Normal approximation through data replication when estimating DisPMO, DePMO, left-side and right-side Sigma levels from non-normal data : Table of Contents

Djoko Setijono — Mon Mar 15 02:05:42 GMT 2010

Abstract:
Purpose – This paper seeks to present a way of estimating DisPMO, DePMO, left-side and right-side Sigma levels (as the “mutations” of DPMO and Sigma level when applied on customer satisfaction measurements), where all critical attributes (CTQs) contain data sets that are non-normally distributed. Design/methodology/approach – The calculation of DisPMO, DePMO, left-side and right-side Sigma levels is based on dynamic-multiple CTQs without the need for assuming 1.5 Sigma shift from the mean. Using step-wise multiple regression, CTQs are then the attributes that significantly influence overall customer satisfaction. This further developed method no longer takes normality assumption for granted, which means that, prior to calculating DisPMO, DePMO, left-side and right-side Sigma levels, the data should be proven as being normally distributed. To fulfil the assumption of normality, the primary data are being “replicated” by first generating random numbers that follow normal standard distribution and then adjusting (re-calculating) these random numbers with the mean, standard deviation, and the skewness of the primary data. Simulation technique is then applied to generate a larger amount of secondary data as the basis for estimating DisPMO, DePMO, left-side and right-side Sigma levels. Findings – The application of the method in a Swedish house-building construction project suggests that: the use of multiple CTQs may reduce the risk for under-/overestimation of Sigma levels, and DisPMO and DePMO are each other's “mirror” and both of them should be considered when calculating Sigma levels. The calculated Sigma levels suggest that the developer's performance is still quite far below Six Sigma level of performance. Originality/value – Using the replica of the primary data as a way of approaching normality may be regarded as the main contribution of the paper in addressing one of the challenges in Six Sigma theory.

Comparative evaluation of critical factors in delivering service quality of banks: An application of dominance analysis in modified SERVQUAL model : Table of Contents

Mukesh Kumar, Fong Tat Kee, Vincent Charles — Mon Mar 15 02:05:42 GMT 2010

Abstract:
Purpose – This study aims to find the differences in the service quality (if any) between two types of banks, namely conventional and Islamic, in terms of common critical factors after re-examining the SERVQUAL model, originally pioneered by Parasuraman. Further, the technique of dominance analysis is used to examine the relative importance of the critical factors in closing up the overall service quality gap in these two types of banks. Design/methodology/approach – The sample is made up of 308 bank customers, consisting of the customers from both Islamic and conventional banks from different parts of Malaysia. The data have been collected by using the structured questionnaire, which consists of three parts. Part 1 deals with consumers' usage of banking channels and their banking behaviour. Part 2 contains 26 statements related to service quality dimensions based on past literature. Finally, Part 3 contains the questions related to the socio-demographic profiles of respondents. Findings – The modified SERVQUAL model consists of four critical factors (dimensions) as detected by factor analysis: tangibility, reliability, competence, and convenience. The results reveal that the expectations on competence and convenience are significantly different between conventional banks and Islamic banks, whereas the perceptions on tangibility and convenience are found to be significantly different between these two types of banks. The application of dominance analysis in the SERVQUAL model indicates that the difference between the two types of banks is in terms of degree and not pattern. Competence and convenience are found to be the relatively more dominating factors in both the types of banks. These two dimensions together can help to reduce the overall service quality gap to an extent of 72 per cent in the case of conventional banks and 85 per cent in the case of Islamic banks. Originality/value – The application of dominance analysis in the SERVQUAL model could be more meaningful in determining the relative importance of the factors when dimensions are interdependent. It permits direct comparison of measures and allows one to predict the level of influence of one factor in comparison with other factors. The study could be quite useful from the policy perspective in providing the guidelines to develop proper strategies and acknowledge the changes in customers' banking behaviour more quickly.