Browsing by Author "KOTZ, S"

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DISTRIBUTIONAL AND INFERENTIAL PROPERTIES OF PROCESS CAPABILITY INDEXES
(1992-10-01)
PEARN, WL
;
KOTZ, S
;
JOHNSON, NL
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工業工程與管理學系
;
Department of Industrial Engineering and Management
In this paper we survey and critically comment on some basic concepts and notions relevant to the methodology dealing with process capability indices (PCI's). The emphasis is on distributional and inferential aspects. The intent is to contribute to the understanding and interpretation of these indices, if one is (unfortunately) required to use them. We regard them primarily as indicators of the expected proportion of nonconforming items, and not as having some relationship to arbitrary loss functions, as is currently the more fashionable viewpoint. New PCI's, related to the expected proportion of nonconforming items, are suggested.
SOME PROCESS CAPABILITY INDEXES ARE MORE RELIABLE THAN ONE MIGHT THINK
(1993)
KOTZ, S
;
PEARN, WL
;
JOHNSON, NL
;
交大名義發表
;
National Chiao Tung University
In this paper we obtain formulae for exact expected values and standard deviations of estimators of certain process capability indices discussed by Bissell. In particular, we show that for the index C(pk) Bissell's formula gives values for the standard deviation which are too high especially when the actual population mean value is close to (or equal to) the average of the upper and lower specification limits.