When learning about Six Sigma, it may help to consider these charts, which detail how sigma level relates to defects per million opportunities (DPMO), and some real-world examples.

Sigma Performance Table

Sigma Performance Levels – One to Six Sigma
Sigma Level Defects (or Errors) Per Million Opportunities (DPMO) Yield (or Produced or Delivered) Correctly (%)
1 691,462 30.85
2 308,538 69.146
3 66,807 93.319
4 6,210 99.379
5 233 99.9767
6 3.4 99.9997

What Would Sigma Values Look Like In The Real World?

It’s one thing to see the numbers and it’s a whole other thing to see how it would apply to your daily life.

Real-world Performance Levels
Situation or Example In 1 Sigma World In 3 Sigma World In 6 Sigma World
Pieces of your mail lost per year [assuming 1,600 opportunities per year] 1,106 107 Less than 1
Number of aircraft takeoff or landing incidents [assuming one takeoff and landing per flight, round trip] 25 times per 10 flights 24 times per 100 flights 12 times per million flights
Number of empty coffee pots at work (who didn’t fill the coffee pot again?) [assuming 680 opportunities per year] 470 45 Less than 1
Number of telephone disconnections [assuming 7,000 talk minutes] 4,839 467 0.02
Erroneous business orders [assuming 250,000 opportunities per year] 172,924 16,694 0.9
Electricity outage [assuming 30 day month = 720 hours] 500 hours 45 hours 9 minutes

In the United States alone if the sigma level were between 3 and 4, there would be 50 newborn babies dropped per day and 5,000 incorrect surgical procedures per week.

Not all opportunities and defects are created equal. I think all flight passengers would agree that a flight delay is less worrisome than a flight incident on landing.

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