Six sigma understanding 

 

What is six sigma?

• Six sigma is a measurement scale upon which improvement / performance can be gauged or overall methodology that provides standardized problem-solving tools improvement.
• What is six sigma mean?
• To understand sigma, basic statistic term is must. Sigma actually is standard deviation. Six sigma mean a process with 2Cpk, or say that 0.001ppm (0.001 defect / error found out of 1 million). However, six sigma implemented by Motolora which used in manufacturing is actually 1.5 sigma shifted. It means that for the six sigma qualified process is actually 4.5 sigma in statistic, which is represent 1.5 Cpk or 3.4ppm.
• Six Sigma Basic Statistical Introduction
• What is process sigma about?
• Process sigma is a possibility, a possibility that error/defect occur in the manufacturing process.
• Necessary to achieve six sigma?
• It depends on the customer requirement. The specification provided by customer directly affect the process sigma.
• How many sigma are required in the manufacturing process?
• It depends on the customer requirement. Six sigma company will provide the requirement on either Cpk or PPM to the supplier.
• Below is the conversion table

Above table is traditional six sigma conversion. However, the modern six sigma, 1.5 sigma shifted allowed. Use the microsoft excel formula convert sigma process and the Cpk and ppm

Excel formula for ppm = (1-NORMDIST(sigma,0,1,1))*1000000 where replace the sigma with the number of the process sigma. The result is showing traditional sigma ppm. For the modern sigma ppm, formula == (1-NORMDIST(sigma-1.5,0,1,1))*1000000

Cpk = sigma/3

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• More Topic
• Six sigma basic statistical introduction
  Six sigma process
  Six sigma distribution and possibility