# Estimating and testing process accuracy with extension to asymmetric tolerances

Estimating and testing process accuracy with extension to asymmetric tolerances Pearn et al. (Commun. Stat. Theory Methods, 27(4):985–1000, 1998) introduced the process accuracy index C a to measure the degree of process centering, the ability to cluster around the center. In this paper, we derive an explicit form of the cumulative distribution function for the estimator $${\hat{C}_a }$$ with the case of symmetric tolerances. Subsequently, the distributional and inferential properties of the estimated process accuracy index C a are provided. Calculations of the critical values, P-values, and lower confidence bounds are developed for testing process accuracy. Further, a generalization of C a for the case with asymmetric tolerances is proposed to measure the process accuracy. Based on the results practitioners can easily perform the testing of the process accuracy, and make reliable decisions on whether actions should be taken to improve the process quality. An application is given to illustrate how we test the process accuracy using the actual data collected from the factory. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Quality & Quantity Springer Journals

# Estimating and testing process accuracy with extension to asymmetric tolerances

, Volume 44 (5) – May 9, 2009
11 pages

/lp/springer_journal/estimating-and-testing-process-accuracy-with-extension-to-asymmetric-DkWAHy4M1k
Publisher
Springer Netherlands
Subject
Social Sciences; Methodology of the Social Sciences; Social Sciences, general
ISSN
0033-5177
eISSN
1573-7845
D.O.I.
10.1007/s11135-009-9243-x
Publisher site
See Article on Publisher Site

### Abstract

Pearn et al. (Commun. Stat. Theory Methods, 27(4):985–1000, 1998) introduced the process accuracy index C a to measure the degree of process centering, the ability to cluster around the center. In this paper, we derive an explicit form of the cumulative distribution function for the estimator $${\hat{C}_a }$$ with the case of symmetric tolerances. Subsequently, the distributional and inferential properties of the estimated process accuracy index C a are provided. Calculations of the critical values, P-values, and lower confidence bounds are developed for testing process accuracy. Further, a generalization of C a for the case with asymmetric tolerances is proposed to measure the process accuracy. Based on the results practitioners can easily perform the testing of the process accuracy, and make reliable decisions on whether actions should be taken to improve the process quality. An application is given to illustrate how we test the process accuracy using the actual data collected from the factory.

### Journal

Quality & QuantitySpringer Journals

Published: May 9, 2009

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