Real Life Sigma Level Examples
In Six Sigma, you can summarize the success rate of a process metric into something called a sigma level. In most processes, a process performing at “6 sigma” is considered excellent, but might be unrealistic for some processes (hiring employees), and not good enough for other processes (like airline safety).
But striving to hit 6 sigma performance is not as important as improving from where you are today. If you’re at 2 sigma, try and move to 3 sigma. If you’re already at 7 sigma, why not 8 sigma?
Here are some examples of processes and their sigma level, along with the number of incidents that would happen out of one million chances.
Use the iSixSigma Process Sigma Calculator to compare your process
| Metric | Incidents per million | Incident Rate % | Sigma Level |
| Single airline fatality (1993-2012) | 0.2 | 0.00002% | 6.56 |
| Fraudulent voters in State of Iowa elections (2018) | 27 | 0.0027% | 5.54 |
| Medical specimens not meeting transportation conditions required for testing | 51 | 0.005% | 5.39 |
| Trash hauler fatal injuries per full-time equivalent worker (2014) | 358 | 0.04% | 4.88 |
| Lost luggage on major US airlines (2012) | 3,090 | 0.3% | 4.24 |
| COVID-19 death rate of health care personnel cases (Aug 2020) | 4,595 | 0.46% | 4.10 |
| Patients found without identification bands | 5,265 | 0.5% | 4.06 |
| Duplicate medical test orders | 15,200 | 1.5% | 3.66 |
| Healthcare specimen redraws | 19,053 | 1.9% | 3.57 |
| Contamination level of recycling shipped to China | 20,000 | 2.0% | 3.55 |
| Illness or injury per Materials Recovery Facility (MRF) worker (2017) | 98,000 | 9.8% | 2.79 |
| Oregon recycling rate of beverage containers covered by its bottle deposit system (2018) | 100,000 | 10.0% | 2.78 |
| Inbound Recycling Contamination Rates (2019) | 169,000 | 16.9% | 2.46 |
| Therapeutic drug monitoring timing | 244,000 | 24.4% | 2.19 |
| Manitoba (Canada) material lost recovery rates (2016) | 300,000 | 30.0% | 2.02 |
| Electronics shipped to developing nations for recycling that end up in the landfill (2016) | 310,000 | 31.0% | 1.99 |
| Patient compliance to anticoagulation therapeutic range for single clinic (2015) | 543,698 | 54.3% | 1.39 |
| Trash not recycled in the United States (2014) | 654,000 | 65.4% | 1.10 |
