The Relation between the Process Capability Index and the Quality Assurance Level Considering Various Conditions

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Journal of Korean Society for Quality Management > Volume 30(2); 2002 > Article

Journal of Korean Society for Quality Management 2002;30(2): 130-.

다양한 상황을 고려한 공정능력지수와 품질보증수준의 관계

조문수, 임태진

숭실대학교 산업·정보시스템공학과

The Relation between the Process Capability Index and the Quality Assurance Level Considering Various Conditions

ABSTRACT

This paper investigates the relation between the Process capability index(PCI) and the quality assurance level under various conditions. The effect of the off-targetness of the process mean, deviation from the nomality, the estimation error, and tile measurement error on the quality assurance level is evaluated. Various distributions such as the Student-t, the chi-square, the gamma, the Weibull, and the log-normal distributions are considered to evaluate the deviation from the nomality. The quality levels under abnormal conditions turn out to be severely different from that under the standard condition. We provide tables and graphs of the quality assurance level on various abnormal conditions. In order for the industry users to use the PCI properly, they should refer to the tables and graphs, especially when they are not certain about the standard assumptions on which the PCI depends.

Key Words: Process Capability Index;Quality Assurance Level;