Abstract

It is generally accepted that variability is one of quality’s greatest threats, and consequently, the purpose of most quality tools, including Six Sigma, is to reduce variability. The sigma metric measures process performance and is often compared to process capability indexes. Six Sigma books discuss the advantages of the sigma metric, but this study lists a number of disadvantages not mentioned in the literature and notes that not all supposed advantages are truly advantageous. To correct this situation, the authors provide corrective actions that should be taken.