An asymptotic confidence interval for the process capability index C_(pm)

摘要

The use of indices as an estimation tool of process capability is long-established among the statistical quality professionals. Numerous capability indices have been proposed in last few years. C-pm constitutes one of the most widely used capability indices and its estimation has attracted much interest. In this paper, we propose a new method for constructing an approximate confidence interval for the index C-pm. The proposed method is based on the asymptotic distribution of the index C-pm obtained by the Delta Method. Under some regularity conditions, the distribution of an estimator of the process capability index C-pm is asymptotically normal.