Key Points
- The Sigma Level corresponds to the likelihood of defects present in a process.
- 1 Sigma is the absolute lowest level, with 31% of the yield being free of defects.
- 6 Sigma is the highest, with over 99% of the yield being free of defects.
- Organizations should strive for 6 Sigma, but can readily attain 5 Sigma.
- Organizations with a 4 Sigma or lower have some serious work to do to iron out their process issues.
When learning about Six Sigma, it may help to consider these charts. These detail how Sigma Performance Levels relate to defects per million opportunities (DPMO), and some real-world examples.
Sigma Performance Levels 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. It’s a whole other thing to see how it would apply to your daily life. Let’s take a closer look at how Sigma Performance Levels correspond with actual real-world examples.
| Real-world Performance Levels | |||
|---|---|---|---|
| Electricity outage [assuming 30-day month = 720 hours] | 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 |
Think about if in the United States, the Sigma Performance Levels were between 3 and 4. There would be 50 newborn babies dropped per day. It would also come out to 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.
Why It Matters?
So, I don’t have to tell you why having near-perfect production is paramount in your processes. Time spent fixing or addressing defects is time you could spend perfecting processes. Further, if you have defective deliverables, you aren’t listening to the voice of the customer.
The average consumer isn’t going to care about whether or not you’re putting in the work behind the scenes. They care about what is in their possession at the moment. Striving for a higher Sigma Level means you’re maintaining that trust and customer satisfaction, fostering a stable relationship that prevails into the future.
Other Useful Tools
Sigma Level is just one part of the equation when it comes to attaining near-perfection in your processes. Any organization would do well to incorporate some other concepts and tools seen throughout the Six Sigma methodology. With that in mind, you might want to look into how Cpk and Sigma Level relate, especially where production is concerned.
Additionally, if you’re looking to address issues, it helps to have the right tools for the job. If you’re current problem-solving skills aren’t to task, then learning how to utilize the 7 QC tools might be what you need. These are quick and simple tools, but help to iron out any kinks you’re finding in production.
In Summary: Sigma Performance Levels
Understanding Sigma Levels is crucial for maintaining the quality of our processes and their subsequent deliverables. As you can see from the real-world examples, the lower the Sigma Level, the more likely you are to run into grave errors. With that in mind, it’s worth striving for a 6 Sigma in your processes.
