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The Scientific World Journal
Volume 2014, Article ID 275374, 10 pages
Research Article

Parameter Interval Estimation of System Reliability for Repairable Multistate Series-Parallel System with Fuzzy Data

Department of Mathematics, Faculty of Science, King Mongkut's University of Technology Thonburi, Bangkok 10140, Thailand

Received 12 February 2014; Revised 10 April 2014; Accepted 24 April 2014; Published 22 May 2014

Academic Editor: Nirupam Chakraborti

Copyright © 2014 Wimonmas Bamrungsetthapong and Adisak Pongpullponsak. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The purpose of this paper is to create an interval estimation of the fuzzy system reliability for the repairable multistate series–parallel system (RMSS). Two-sided fuzzy confidence interval for the fuzzy system reliability is constructed. The performance of fuzzy confidence interval is considered based on the coverage probability and the expected length. In order to obtain the fuzzy system reliability, the fuzzy sets theory is applied to the system reliability problem when dealing with uncertainties in the RMSS. The fuzzy number with a triangular membership function is used for constructing the fuzzy failure rate and the fuzzy repair rate in the fuzzy reliability for the RMSS. The result shows that the good interval estimator for the fuzzy confidence interval is the obtained coverage probabilities the expected confidence coefficient with the narrowest expected length. The model presented herein is an effective estimation method when the sample size is . In addition, the optimal α-cut for the narrowest lower expected length and the narrowest upper expected length are considered.