Process Capability Indices for Shape Parameter of Weibull Distribution


Process capability analysis is used to determine the process performance as capable or incapable within a specified tolerance. Basic indices Cp, Cpk, Cpm, Cpmk 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.

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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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