Six Sigma Exchange provides you all of the basics of understanding Six Sigma methodology.
Six Sigma is used to analyze, test, and improve processes (whether manufacturing or service oriented). The name comes from the original Six Sigma professionals that aimed to have no more than 3.4 defects per million units produced.
Sigma is the greek letter used in statistics to represent a standard deviation from a population or sample mean. Six Sigma refers to six standard deviations above the mean (in the case of a process where you are concerned with defects which occur above an upper specification limit.) If you have a population of one million, on average only 3.4 data points fall above six sigma*. Thus, if a process is “Six Sigma,” generally that will mean that the process produces the equivalent of no more than 3.4 failures or defects per one million units.
The methodology applies several steps generally known as DMAIC.
Define the problem (e.g., process is out of specified range.)
Measure key internal processes critical to quality.
Analyze why defects occur.
Improve the process to stay within tolerance.
Control the process to stay within goals.
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