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Sigma is the Greek letter assigned to represent standard deviation; that is, the amount of variation within a given process. The number of Sigma can be "fit" between the gap of process mean and the upper or lower specification limit, determine the defect level of a process. The higher the Sigma level, the lower the number of defect. Statistically, a process that achieving Six Sigma (6) level of quality equates to a mere 3.4 defects out of one million opportunities, or nearly defect free performance.

The roots of Six Sigma as a measurement standard can be trace back to Carl Frederick Gauss (1777-1855) who introduced the concept of the normal curve. Application of statistic in process control was first introduce by Walter Shewhart 1920's, shows that three sigma from the mean is the point where a process requires correction. Many measurement standards (Cpk, Zero Defects, etc.) later came on the scene but credit for coining the term "Six Sigma" goes to a Motorola engineer named Bill Smith ( www.isixsigma.com )

To achieve the Six Sigma quality level, Motorola developed the DMAIC (Define, Measure, Analyze, Improve, Control) strategy that consistently reduce variation exist in the manufacturing process. The DMAIC quality improvement strategy help Motorola win the prestigious Malcolm Baldrige National Quality Award in 1988, after two years of Six Sigma deployment ( www.isixsigma.com ).

"Six Sigma" has replaced the good name of DMAIC. The Six Sigma that make known to the industries today is a set of quality management tools. It has developed into a strategic quality program that stresses the application of statistical and problem solving technique in a methodical and systematic manner ( Zu XX, 2005).

Six Sigma today is a systematic problem solving methodology that uses data and statistical analysis to measure and identify process variation. Process variation or defect can be identify and eliminate with appropriate correction action. A process that achieving Six Sigma level when the defective rate lesser than 3.4 units per million opportunities. Six Sigma can be defined and understood at three distinct levels:

a)Metric something measurable for any process
b)Methodology a set of systematic problem solving approach
c)Philosophy the culture

Motorola scored more than $16 billion saving from the Six Sigma deployment. ( Zu XX, 2005), GE Healthcare report more than $3 billion saving from the Six Sigma program and 20% in business efficiency improvement (Walter H. 2001). Many American companies try to adopt the quality improvement strategy after Motorola's announcement. Today, Six Sigma has been successfully adopted by many company including GE, Honeywell, Sony, Caterpillar, Kodak, Texas Instruments, Jaguar, Ford, TRW, Delphi, Raytheon, Lockheed-Martin, Boeing, Dupont, Polaroid, 3M, and Johnson Controls ( Zu XX, 2005).

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