EasyProblemSolving
Six Sigma
Measure, reduce variation & improve
What is Six Sigma
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a statistical measure of process capability
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a set of tools and techniques for reducing variation
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a philosophy about operational excellence
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A Measurement Scale which compares the output
of a process to customer requirements
Its all about continuous improvement by reducing variation
What is Variation
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as a customer you want consistency in any product or service that you consume
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variation causes dissatisfaction or defect
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defect - any thing that doesnt meet customer expectation
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we generally measure process performance as an average v/s some target
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average would hide the variation between data points
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example - average of 4 cars' speed 25, 50 , 75 & 100 is 62.5 , does this show or hide the difference between each car ?
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So variation should be measured
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we measure variation via (depending on the data distribution)
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Standard deviation ​
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Range
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Inter quartile range
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Basic premises underlying six sigma
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All processes have variability
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Variability has definable causes
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Typically only a few causes are significant
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If causes can be identified & understood, they can be controlled
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Design must be robust to the effects of remaining process variations
6 sigma a measure of performance
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6 sigma = 6 σ ; σ is Greek letter s
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σ denotes standard deviation - average distance of data points in a set from the mean (average)
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Standard deviation shows variation from mean & your mean should be near or on the target
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Smaller the standard deviation ; lesser the variation
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So if your data sets' variation, denoted by σ, is small enough, you would be able to put 6 σ (six std deviations) between the target and customer specifications
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This can also be denoted as DPMO - defects per million opportunities ; so 3.4 DPMO would denote a 6σ level performance
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3.4 DPMO = 99.99666% = 6σ