A Note on 1.5 Sigma Shift in Performance Evaluation

Abstract

Understanding variation is critical to quality (CTQ) of product or service delivery, which is the key to success. Six Sigma is the business process improvement strategy that extensively focuses on variation reduction thereby reducing number of defects. One of the major constituents of Six Sigma definitions is 1.5 sigma shift, which is attributable to random error. It is not possible to understand Six Sigma thoroughly by overlooking the concept of 1.5 sigma shift. A conventional 3.4 defect per million opportunity (DPMO) capability of Six Sigma process is based on 1.5 sigma shift. This paper aimed at explaining ancestry of 1.5 sigma shift in connection with quality engineering methods. Origin of 1.5 sigma shift factor with reference to producibility analysis, worst-case sampling error and other quality engineering methods has been discussed in this paper.