Obtaining confidence intervals for C-pk using percentiles of the distribution of (C)over-cap(p)

    Authors

    L. L. Hoffman

    Comments

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    Abbreviated Journal Title

    Qual. Reliab. Eng. Int.

    Keywords

    process capability index; simulation; inverse chi-square; CAPABILITY INDEXES; Engineering, Multidisciplinary; Engineering, Industrial; Operations; Research & Management Science

    Abstract

    (C) over cap (pk) is used as an estimate of process capability and can reflect performance degradation due to both shifts in the process mean and variability. Exact upper and lower confidence limits for the actual parameter value an elusive. Objections to existing estimators focus on two areas: the difficulty of executing the needed computations and the excessive widths of those confidence bounds. The CPE estimator (so called since it relies on (C) over cap (p)) which we derive in this paper is formed by simply multiplying (C) over cap (pk) by a value from the inverse chi-square distribution. A PASCAL computer program is supplied which generates those percentiles. Our CPE is compared via simulation to other estimators and is shown to be the preferred selection in most cases by providing the requisite probability coverage and narrow interval widths. Copyright (C) 2001 John Wiley & Sons, Ltd.

    Journal Title

    Quality and Reliability Engineering International

    Volume

    17

    Issue/Number

    2

    Publication Date

    1-1-2001

    Document Type

    Article

    Language

    English

    First Page

    113

    Last Page

    118

    WOS Identifier

    WOS:000168447800006

    ISSN

    0748-8017

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