Learn Six Sigma from first principles, understand White, Yellow, Green, Black and Master Black Belt roles, explore practical examples, calculate DPMO and capability, and build a structured DMAIC improvement project with portable JSON save/load and a professional printable report.
Improvement begins with the Voice of the Customer and converts needs into measurable Critical-to-Quality requirements.
Two processes can have the same average but very different spread. Six Sigma seeks stable, centred and capable performance.
Projects should connect defects and delays to customer impact, risk, capacity, cost of poor quality and measurable benefit.
| Sigma level | Indicative DPMO | Indicative yield | Interpretation |
|---|---|---|---|
| 1σ | 691,462 | 30.85% | Very poor and highly variable process. |
| 2σ | 308,538 | 69.15% | Frequent defects and major improvement need. |
| 3σ | 66,807 | 93.32% | Often still unacceptable for safety-critical or high-volume work. |
| 4σ | 6,210 | 99.379% | Strong performance, but thousands of defects may still occur at scale. |
| 5σ | 233 | 99.9767% | Very capable performance. |
| 6σ | 3.4 | 99.99966% | Conventional long-term Six Sigma benchmark using the 1.5σ shift assumption. |
DPMO depends on how a defect opportunity is defined. Compare like-for-like processes and avoid inflating opportunity counts merely to improve the metric.
State the problem, customer impact, business case, scope, team, goal and project charter.
Define operational measures, validate the measurement system, map the process and establish baseline performance.
Use evidence to identify vital causes, separate correlation from causation and verify the root cause.
Generate, evaluate, trial and implement solutions that address verified causes and manage implementation risks.
Standardise controls, assign ownership, monitor performance, react to deterioration and confirm sustained benefits.
Define, Measure, Analyse, Design and Verify is often used for new products, services or processes when incremental improvement is insufficient.
Role: Awareness and participation.
Role: Active project team member.
Role: Part-time improvement project leader.
Role: Advanced or full-time improvement specialist.
Role: Programme expert and coach.
Role: Senior business sponsor.
| Area | Green Belt | Black Belt |
|---|---|---|
| Typical commitment | Part-time alongside normal role. | Substantial or full-time improvement responsibility. |
| Project scope | Departmental or moderately cross-functional. | Complex, strategic and cross-functional. |
| Statistics | Descriptive statistics, MSA, capability, basic tests and SPC. | Advanced inference, regression, ANOVA, DOE and optimisation. |
| Leadership | Facilitates a project team and local stakeholders. | Leads major change, coaches belts and influences senior stakeholders. |
| Example | Reduce inspection queue time by 40%. | Redesign an end-to-end order fulfilment process across multiple sites. |
Problem: Hydrogen-embrittlement failures following electroplating.
Measure: hardness, cleaning time, plating thickness, bake delay, bake duration and oven uniformity.
Analyse: failures strongly associated with excessive delay before embrittlement-relief baking.
Improve: timed transfer, visual escalation and capacity protection.
Control: electronic timestamp, oven chart review and layered audit.
Problem: adhesion failures after environmental exposure.
Measure: substrate cleanliness, humidity, pretreatment age, wet-film thickness and cure profile.
Analyse: failures cluster at high humidity and incomplete cure.
Improve: environmental interlock and validated cure window.
Control: SPC for cure temperature and reaction plan for excursions.
Problem: customer support calls average 18 minutes.
Analyse: repeated searching for product information is the largest delay.
Improve: searchable knowledge base and standard troubleshooting path.
Result: average call duration reduced to 9 minutes.
Problem: emergency patient waiting time averages 110 minutes.
Analyse: triage is the dominant bottleneck.
Improve: revised triage staffing and electronic pre-registration.
Result: average waiting time reduced to 35 minutes.