On the reliability of the estimated incapability index

摘要

Greenwich and Jahr-Schaffrath (1995) introduced the process incapability index C_pp = C_ip + C_ia, which provides an uncontaminated separation between information concerning the process precision (C_ip) and process accuracy (C_ia). In this paper, we consider the tree indices, and investigate the statistical properties of their natural estimators. For the three indices, we obtain their UMVUEs and MLEs, and compare the reliability of the two estimators based on the relative mean square errors.