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A transformation technique to estimate the process capability index for non-normal processes

journal contribution
posted on 2009-01-01, 00:00 authored by Seyedehzahra Hosseinifard, B Abbasi, S Ahmad, M Abdollahian
Estimating the process capability index (PCI) for non-normal processes has been discussed by many researches. There are two basic approaches to estimating the PCI for non-normal processes. The first commonly used approach is to transform the non-normal data into normal data using transformation techniques and then use a conventional normal method to estimate the PCI for transformed data. This is a straightforward approach and is easy to deploy. The alternate approach is to use non-normal percentiles to calculate the PCI. The latter approach is not easy to implement and a deviation in estimating the distribution of the process may affect the efficacy of the estimated PCI. The aim of this paper is to estimate the PCI for non-normal processes using a transformation technique called root transformation. The efficacy of the proposed technique is assessed by conducting a simulation study using gamma, Weibull, and beta distributions. The root transformation technique is used to estimate the PCI for each set of simulated data. These results are then compared with the PCI obtained using exact percentiles and the Box-Cox method. Finally, a case study based on real-world data is presented.

History

Journal

International journal of advanced manufacturing technology

Volume

40

Pagination

512 - 517

Publisher

Springer

Location

Berlin, Germany

ISSN

0268-3768

eISSN

1433-3015

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal; C Journal article

Copyright notice

2008, Springer-Verlag London