Process Capability Indices for Shape Parameter of Weibull Distribution

Suboohi Safdar; Ejaz Ahmed

doi:10.4236/ojs.2014.43020

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Open Journal of Statistics > Vol.4 No.3, April 2014

Process Capability Indices for Shape Parameter of Weibull Distribution ()

College of Computer Science and Information Systems, Institute of Business Management, Karachi, Pakistan.
Department of Statistics, University of Karachi, Karachi, Pakistan.

DOI: 10.4236/ojs.2014.43020 PDF HTML XML 4,448 Downloads 6,636 Views Citations

Abstract

Process capability analysis is used to determine the process performance as capable or incapable within a specified tolerance. Basic indices C_p, C_pk, C_pm, C_pmk initially developed for normally distributed processes showed inappropriate for processes with non-normal distributions. A number of authors worked on non-normal distributions which were most notably those of Clements, Pearn and Chen, Montgomery and Johnson-Kotz-Pearn (JKP). Obtaining PCIs based on the parameters of non-normal distributions are completely disregarded and ignored. However parameters of some non-normal distributions have significance for knowing the status of process as capable or incapable. In this article we intend to work on the shape parameter of Weibull distribution to calculate PCIs. We work on two data sets for verification and validation purpose. Efficacy of the technique is assessed by bootstrapping the results of estimate and standard error of shape parameter.

Keywords

Regression Coefficient; Non-Normal Distribution; Delta Method; Bootstrapping

Share and Cite:

Safdar, S. and Ahmed, E. (2014) Process Capability Indices for Shape Parameter of Weibull Distribution. Open Journal of Statistics, 4, 207-219. doi: 10.4236/ojs.2014.43020.

Conflicts of Interest

The authors declare no conflicts of interest.

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