Six Sigma
Definition
Six Sigma
Six Sigma is a data driven quality method that cuts process variation to under 3.4 defects per million opportunities. Motorola built it in 1986, and Fortune 500 firms still use it today to trim waste, shorten cycles, and lift customer loyalty.
The method blends statistics with process discipline. Its threshold treats any output beyond six standard deviations of the mean as a defect, so teams shrink variation instead of nudging averages.
Put another way, 3.4 defects per million opportunities (DPMO) works out to roughly one failure in every 294,000 chances to fail. That is the arithmetic behind the name.
Most buyers meet Six Sigma through a vendor’s quality pitch. A provider that runs quality assurance on gut feel will describe defects in adjectives — a Six Sigma shop describes them in counts per million.
Key takeaways
- Six Sigma targets fewer than 3.4 defects per million opportunities, or 99.99966 percent accuracy.
- DMAIC (Define, Measure, Analyze, Improve, Control) is the core problem-solving cycle.
- Belt levels (Yellow, Green, Black, Master Black) set practitioner authority and project scope.
- Lean Six Sigma merges the method with lean production to cut non-value time as well.
- Adoption spans manufacturing, healthcare, finance, and Business Process Outsourcing (BPO) service operations.
How it works
Six Sigma works by pushing a defined problem through five gated stages known as DMAIC. Teams set a baseline, hunt root causes with statistical tools, pilot one change, then lock the gain with control charts and standard work.
DMAIC covers Define, Measure, Analyze, Improve, and Control. Each stage carries gated deliverables, so a project cannot advance until the data supports it.
That gating is what separates Six Sigma from softer business process improvement programs. You do not get to skip Measure because the fix looks obvious.
Control is the phase most programs botch. Without a control chart and a named process owner, the gain drifts back and the savings quietly reverse. Auditors look for that owner before they check the baseline math.
Practitioners hold belt certifications that mirror martial arts ranks. Yellow Belts assist, Green Belts run tactical projects, and Black Belts lead cross-functional initiatives — Master Black Belts coach the coaches and steward the training curriculum.
| Belt | Typical role | Project scope | Typical training load |
|---|---|---|---|
| Yellow | Team member | Local task fixes | short awareness course |
| Green | Project lead | Departmental process | 5 to 10 days plus a 3 to 6 month project |
| Black | Full-time lead | Cross-functional initiative | roughly 10 further days plus a larger project |
| Master Black | Program mentor | Training and portfolio strategy | 2 to 3 years of program leadership |
Two standards pin the method down. The International Organization for Standardization (ISO) issues both: ISO 13053 sets out the DMAIC project method, and ISO 18404 defines competency requirements for Black Belt, Green Belt and Lean practitioner roles.
A landmark report from the American Society for Quality (ASQ) tallied Motorola’s cumulative Six Sigma savings at more than 17 billion dollars by 2005. Spread across those 19 years, that averages roughly 900 million dollars a year.
Examples
Six Sigma shows up in four well documented programs: manufacturing at Motorola and General Electric, retail banking at Bank of America, and hospital care at Mount Carmel Health System. The pattern holds across all four.
| Organization | Years | Reported result |
|---|---|---|
| Motorola | 1986 to 2005 | more than 17 billion dollars in cumulative savings |
| General Electric | 1995 to 2000 | 12 billion dollars in gains within five years |
| Bank of America | 2001 to 2004 | roughly 2 billion dollars in added revenue |
| Mount Carmel Health System | 2000 to 2002 | medication errors down 71 percent |
Motorola is the origin story. Engineers there built Six Sigma in 1986 to attack defect rates on the company’s manufacturing lines, and Motorola kept reporting against the 3.4 target for nearly two decades afterwards.
General Electric adopted Six Sigma under Jack Welch in 1995 and reported 12 billion dollars in gains within five years, according to the company’s annual reports. The push reset how large conglomerates budgeted for quality.
Bank of America rolled Six Sigma into retail branch operations in 2001, trimming customer defection rates and adding roughly 2 billion dollars in revenue over the next three years. Financial services still run the DMAIC playbook on back office remediation.
Mount Carmel Health System in Ohio ran Six Sigma projects from 2000 to 2002 and cut medication errors by 71 percent, one of the earliest documented hospital wins. Hospital adoption has climbed steadily since.
BPO providers apply Six Sigma to voice queues and back office queues alike. A Black Belt project at a Manila call center can shave 15 to 20 seconds off average handle time, which flows straight into the client’s per seat rate.
Take a five minute average call as an illustration — trimming 15 seconds is a 5 percent capacity gain, and on a 200 seat floor that frees the equivalent of ten seats without hiring anyone.
Related terms
The cluster around Six Sigma covers process governance, quality control, and lean methods. Each term overlaps at one specific stage, so knowing where the tools diverge keeps teams from stacking two initiatives that do the same job twice.
- Lean Methodology: waste-focused sibling that pairs with Six Sigma for combined variation and speed gains.
- Business Process Management: umbrella discipline that hosts Six Sigma projects inside broader workflow governance.
- Kaizen: continuous small-improvement cadence popular in lean shops, less statistical than Six Sigma.
- Total Quality Management: the 1980s predecessor Six Sigma refined into a metrics-driven form.
- Process Improvement: plain-language category all these methods sit under.
- Quality Assurance: compliance-facing cousin focused on standards adherence rather than variation reduction.
FAQ
Common questions about Six Sigma cover what it measures, what certification costs in time, and how it differs from lean or the ISO standards. These are the points buyers raise when scoping a program with a provider.
What does Six Sigma actually measure?
It measures process variation, expressed as defects per million opportunities. Hitting six sigma means the process runs at 99.99966 percent accuracy, or 3.4 defects per million. The threshold assumes a normal statistical distribution.
How long does Six Sigma certification take?
Green Belt training usually runs 5 to 10 days plus a project of 3 to 6 months. Black Belt certification adds roughly another 10 days of coursework and a larger project. Master Black Belt status normally takes 2 to 3 years of program leadership.
Is Six Sigma the same as lean?
No — lean removes waste and non-value time, while Six Sigma removes variation and defects. Lean Six Sigma combines both under one project charter and is the version most BPO clients buy today.
Does ISO recognize Six Sigma?
Yes. ISO 13053 defines the Six Sigma project method, and ISO 18404 sets competency levels for Black Belt, Green Belt and Lean practitioner roles. A provider claiming ISO alignment should be able to name which of the two it works to.
What industries use Six Sigma most?
Manufacturing, finance, healthcare, and BPO services dominate the certification rolls. A 2024 McKinsey survey still placed process quality among the top three operations priorities, with Six Sigma the default toolkit.
Can a small BPO afford Six Sigma?
Yes, because a single Green Belt project costs a few thousand dollars in training plus the practitioner’s time, and most Manila and Cebu providers recover that inside one quarter through shorter handle times and less rework.
For a shortlist of Six Sigma certified providers and the rates they quote, start on the OA site.
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