The performance of process capability index csOn Skewed Distributions
Title:
The performance of process capability index csOn Skewed Distributions
Author:
Pearn, W. L. Chang, C. S.
Appeared in:
Communications in statistics
Paging:
Volume 26 (1997) nr. 4 pages 1361-1377
Year:
1997
Contents:
Wright considered a new process capability index Cs, which extends the most useful index to date for processes with two-sided specification limits,pmk proposed by Pearn, Kotz and Johnson . The new index Csnot only takes into account the process variation as well as the location of the process mean relative to the specification limits, but also considers the asymmetry of the distribution by incorporating a penalty for skewness. Wright (1995) investigated an estimator of Csand studied its bias and variance by simulation. The simulation study, however, was restricted to normal distributions where skewness is not present. In this paper, we extend Wright's simulation study to cover some skewed distributions including chi-square, lognormal, and Weibull distributions for some parameter values. The results show that the percentage bias of the estimator increases as the skewness coefficient |μ3/σ2| increases. Extensive simulation results, comparisons, and analysis are provided.
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