Capability indices for non-normal populations

Abstract

Most of research work about the use of process capability indices (PCIs), which provide a numerical measure on whether a production process is capable of producing items satisfying the quality requirement preset by the customers, is based on the assumption of its process output being approximately normally distributed populations and PCIs for non-normal populations have been comparatively neglected always. In this paper, we first consider a new family of capability indices to cover non-normal populations and then develop a practical procedure for machinery Co., Ltd. application to compare them with other existing indices. Our results show that the new indices are more reasonable than other existing ones in measuring process capability. In addition, we also consider an estimation method to calculate the proposed new indices, which could measure the process capability ability better.