A research note on the estimated incapability index

Process incapability index, which provides an uncontaminated separation between information concerning the process accuracy and the process precision, has been proposed to the manufacturing industry for measuring process performance. Contributions concerning the estimated incapability index have focused on single normal process in existing quality and statistical literature. However, the contaminated model is more appropriate for real-world cases with multiple manufacturing processes where the raw material, or the equipment may not be identical for each manufacturing process. Investigations based on contaminated normal processes are considered. Sampling distributions and r-th moments of the estimated index are derived. The proposed model will facilitate quality engineers on process monitor and performance assessment.