Chapter 24

Six Sigma


The last decade of the 20th century saw quantum leap in the quality management by creating an appreciation and application of six sigma concept. However, the name “six sigma” which also exists in statistics as 6σ had initially created a misconception that the higher the sigma value in a distribution, the larger the range and hence, the lesser the quality which is far from the truth. Hence, this chapter makes an effort in explaining with illustrations, how “six sigma” is a philosophy, and that the sigma value used in statistics is different from the sigma level used in TQM. Several principles and methodologies of applying this technique are explained.


Defects per million opportunities; Six sigma concept; ...

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