US EPA

459238 

Journal Article 

Fuzzy inference for assessing process lifetime performance 

Chang, JF; Hsu, BM; Shu, MH; Yang, CS 

2007 

3 

6B 

1729-1742 

English 

Process capability studies, which use a capability index to provide numerical measures on whether a process conforms to the capability prerequisite set in the factory, have been successfully applied by companies to compete with and lead high-profit markets by evaluating quality and productivity performance. The lifetime capability index L-tp has been proposed to measure process lifetime performance, wherein the output lifetime measurements are considered precise. In. the present study, we study the More realistic situation where the process lifetime output data are imprecise. Using the approach taken by [4..5] with some modifications, a set of confidence intervals, one on top of the other, is used to Produce the triangular shaped fuzzy number for a fuzzy estimate of the lifetime capability index Ltp. With the sampling distribution used far, the estimation of Ltp, two useful fuzzy inference criteria, the critical value and the fuzzy p-value, are proposed to assess the process lifetime performance based on Ltp. The presented methodology takes into consideration a certain degree of imprecision in the sample data and leads to a three-decision rule with a four quadrants decision-making plot. The fuzzy inference for assessing process lifetime performance is a natural generalization of the traditional test; when data are precise the proposed test is reduced to a classical test with a binary decision. 

lifetime capability index; conforming rate; fuzzy sets; fuzzy; hypothesis testing; fuzzy p-value; critical value; hypotheses; assurance; model; sets