Definition
Six Sigma is a data- and statistics-driven methodology for process improvement. The goal is a process so stable and well centred that the tolerance limits lie six standard deviations from the mean — at most 3.4 defects per million opportunities (DPMO). Projects follow the DMAIC cycle: define, measure, analyse, improve, control.
Quality control & SPC
Each phase has its tools: measure — measurement system analysis and capability; analyse — hypothesis tests, regression, Pareto chart; improve — design of experiments; control — control charts. The sigma level is derived from the defect rate and serves to compare processes.
Six Sigma is often combined with Lean (Lean Six Sigma) — Lean removes waste and shortens lead times, Six Sigma reduces variability. Success rests on projects with measurable financial impact and on people trained at Green Belt and Black Belt levels.
In Statistica
Statistica groups the tools of every DMAIC phase in Statistics → Industrial Statistics & Six Sigma: a sigma-level and DPMO calculator, measurement system analysis, capability, control charts, DOE and Pareto charts, complemented by hypothesis tests and regression from the core modules — in one environment without programming.
Related terms
- Control charts (SPC)A control chart is the basic tool of statistical process control (SPC): it plots measurements over time with a centre…
- Process capability (Cp, Cpk)Capability indices compare process variability with the customer's tolerance limits.
- Design of experiments (DOE)Design of experiments (DOE) is a systematic way to find out, with a minimum of runs, which factors (temperature…
- Measurement system analysis (Gauge R&R)Measurement system analysis (MSA) determines how much of the observed variability is caused by the measurement itself.
- Pareto chartA Pareto chart is a bar chart of causes or defect categories sorted from most to least frequent, with a cumulative-share curve.
Knowledgebase guides
FAQ
- What does a 6σ level mean in practice?
- 3.4 defects per million opportunities, allowing for a long-term mean shift of 1.5σ. Ordinary processes run around 3–4σ, i.e. thousands of defects per million.
- Do I need dedicated Six Sigma software?
- Nothing special — you need statistical software covering MSA, capability, tests, DOE and SPC. Statistica has all of it in one module.
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Quality control & SPC
Updated: September 2026.