Composite Capability Index for Multiple Product Characteristics


Bothe, D. R.   (1999, Marcel Dekker, Inc. and ASQ)   Cedarburg, WI

Quality Engineering    Vol. 12    No. 2
QICID: 13899    December 1999    pp. 253-258
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Article Abstract

[This abstract is based on the author's abstract.] A composite capability index for assessing the quality performance of an entire product is presented. This is motivated by the need to combine the usefulness of the capability indices for individual characteristics with the goal of meeting customer expectation of quality. To construct the composite index, a product capability study first determines the probability that each characteristic of a product is within tolerance. Then the combined probability that all characteristics are within tolerance is calculated. This combined result can be converted into a product Cpk index that measures total customer satisfaction, allows different products to be compared, and permits tracking of capability improvements. The features may be characterized by either variable or attribute data. There is no limit to the number of characteristics that may be combined. The product Cpk concept can be extended to summarize the ability of an entire machining or assembly line to produce products meeting all quality requirements.


Capability study,Customer expectation,Product quality,Quality characteristics,Process capability (Cp)

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