Design of Experiments Guide  • Prospective Sample Size and Power • Sigma Quality Level
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Sigma Quality Level
The Sigma Quality Level feature is a simple statistic that puts a given defect rate on a “six-sigma” scale. For example, on a scale of one million opportunities, 3.397 defects result in a six-sigma process. The computation that gives the Sigma Quality Level statistic is
Sigma Quality Level = NormalQuantile(1 – defects/opportunities) + 1.5
Two of three quantities can be entered to determine the Sigma Quality Level statistic in the Sample Size and Power window:
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Number of Defects
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Number of Opportunities
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Sigma Quality Level
When you click Continue, the sigma quality calculator computes the missing quantity.

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Help created on 9/19/2017