Six sigma

The name six sigma comes from statistics: sigma denotes standard deviation, a measure of variation. In quality management, the term represents an exceptionally capable process. The traditional account describes 99.999998 per cent conforming output and no more than 3.4 defects per million opportunities, although those figures rely on different statistical conventions and should not be treated as interchangeable without stating the assumed process shift. The managerial method seeks to approach this level by understanding, reducing and controlling variation. Better quality and process performance are means to an end; the intended outcome is measurable operational and financial improvement.

When to use it

Use six sigma when an organisation needs to identify the causes of poor operational performance, improve process reliability and translate fewer defects into customer or financial value. A project should have a defined business case, but the claim that management should reject any initiative without at least $175 000 in savings is a legacy rule of thumb, not a universal threshold. Scale the expected benefit to the process, organisation and risk involved.

Six sigma is normally sponsored from the top and delivered through a formal project structure. Leaders communicate the purpose, select priorities and review results, while trained employees conduct the analysis. Common roles include:

Executive management champions

the CEO or other senior leaders who maintain oversight of the project portfolio and remove organisational barriers.

Master black belts

expert practitioners who train black belts, advise teams and support consistent application.

Black belts

project leaders accountable for the complete improvement effort.

Green belts

practitioners who lead part-time or bounded initiatives and implement improvement work.

Project teams

employees who contribute process knowledge and apply the relevant techniques under green-belt leadership.

Each organisation adapts the infrastructure, but effective implementation usually requires:

• Sound understanding of the statistical methods being used.
• Enough time and evidence to define the problem correctly.
• Adequate resources for implementation, not only analysis.
• Visible leadership commitment and active governance.
• Attention to the cultural change that new controls may require.
• A communication plan that explains purpose, progress and consequences.
• Practical training for the people doing the improvement work.
• Black belts who can facilitate across functions as well as analyse data.

Origins

Motorola established six sigma as a corporate quality approach during the mid-1980s. Engineer Bill Smith is widely associated with formulating it, while chief executive Bob Galvin sponsored the organisational commitment and Mikel Harry helped develop the technical method and training infrastructure. The work linked process capability, defect measurement and improvement projects within a managed deployment system rather than treating statistics as an isolated quality exercise. AlliedSignal and General Electric later helped popularise the approach beyond Motorola and reinforced its association with trained project roles and financially accountable improvement.