Probabilistic and membership approaches in the construction of control charts for linguistic data

Abstract

Two approaches for constructing control charts for quality assurance when the observations are in the form of linguistic data are presented. Both approaches are based on fuzzy set theory and use fuzzy subsets to model the linguistic terms used to describe product quality. They differ in the interpretation of the control limits and in the procedure used to reduce the fuzzy subsets to scalars for determining the chart parameters. The results obtained with simulated data suggest that, on the basis of sensitivity to process shifts, the control charts for linguistic data perform better than conventional p control charts. The number of linguistic terms used in classifying the observations was found to influence the sensitivity of these control charts. The transformation method used to obtain the representative values and the amount of fuzziness do not seem to affect the performance of either type of control charts.

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Notes on contributors

TZVI RAZ

TZVI Raz (born 1951) is a senior lecturer at the Department of Industrial and Management Engineering, Ben-Gurion University of the Negev, Beer Sheva, Israel, where he teaches courses in information systems design, microcomputer applications, robotics, and other IE subjects. From 1982 to 1989 he was associate professor of Industrial and Management Engineering at the University of Iowa. He holds a Ph.D. (1982) from the University of Missouri—Columbia, a M.A.Sc. (1979) from the University of Toronto and a B.Sc (1977) from the Technion—Israel Institute of Technology, all in Industrial Engineering, as well as a M.S.P.H. (1982) in Health Services Management from the University of Missouri—Columbia. Dr Raz is a senior member of IIE and an associate editor for IIE Transactions. His work has been published in the Journal of Medical Systems, the Journal of Quality Technology, Computers and Industrial engineering, the International Journal of Production Research, IIE Transactions, and other technical journals.

JYH-HONE WANG

JYH-HONE Wang is a lecturer in the Department of Industrial Engineering at California State University—Fresno. He has a Ph.D (1988) and a M.S. (1986) from the University of Iowa and a B.S. (1982) from Tunghai University in Taiwan, all in Industrial Engineering. He is a member of ASQC, IIE and ORSA and his research has appeared in IEEE Transactions on Reliability, International Journal of Production Research, and other technical journals.