Six Sigma level

The Six Sigma level indicates how consistently a process produces results within customer requirements. Motorola pioneered the metric in the late 1980s, and organisations including General Electric and Honeywell later promoted it widely. The customary goal is no more than 3.4 defects per million opportunities under the standard long-term-shift convention. To illustrate the implied rarity, imagine a goalkeeper playing 50 games in a season and facing 50 shots in every game: at the stated rate, one goal would be conceded roughly every 147 years.

When to use it

• Answer the performance question: “How capable are our processes of delivering error-free work?”
• Evaluate capability within the operational-processes and supply-chain perspective.
• Define the data, formula, reporting cadence and sources required for a process-quality KPI.
• Compare actual performance with an agreed target, benchmark or trend.

Origins

Motorola engineer Bill Smith is credited with introducing Six Sigma as a disciplined method for reducing defects and variation during the mid-eighties. Motorola connected process capability with defects per million opportunities, and General Electric’s later adoption under Jack Welch accelerated international use. The widely quoted defect threshold depends on a conventional long-term sigma shift, so any report should state its opportunity definition and statistical convention.

What it is

Perspective: Operational processes and supply chain perspective.

Key performance question: How capable are our processes of delivering error-free work?

Six Sigma is both a capability measure and an improvement methodology. As a methodology, it organises analysis and change through DMAIC:

Define

internal or external customer requirements and the process outcome expected.

Measure

current performance and establish how frequently defects occur.

Analyse

the evidence and process map to locate causes, patterns and improvement opportunities.

Improve

the selected process by designing and testing ways to remove, correct or prevent the verified problems.

Control

the revised process so that it remains on the intended course.

Organisations commonly deliver DMAIC through trained internal practitioners—Master Black Belts, Black Belts and Green Belts—with responsibilities reflecting their experience and level of involvement.

The proposition is that a more capable process produces fewer customer failures and, when the project addresses a strategically important activity, contributes to stronger and more durable financial results.

How to use it

Measurement

Define the unit, defect and opportunity before collecting data. A sigma result is meaningful only when those definitions are stable and relevant to the customer.

Data collection method