Process performance assessment based on sub-samples – a large sample approach.

Process incapability index has been introduced to provide quantitative measures on process performance. Contributions of the estimated incapability index based on sub-samples have been proposed under the normality assumption. In this paper, investigations based on sub-samples are considered under general conditions having fourth central moment. The limiting distribution of the estimated incapability index based on sub-samples is derived. An approximate 100(1-α)% upper confidence bound of the considered incapability index is constructed. A demonstrated example is also provided to illustrate how the proposed approximate upper confidence bound may be applied for judging whether the process runs under the desirable quality requirement. [ABSTRACT FROM AUTHOR]