God, grant me the serenity to accept the things I cannot change, The courage to change the things I can, And the wisdom to know the difference. (Serenity Prayer, Reinhold Niebuhr)

Six Sigma

Six Sigma is a business management strategy, initially implemented by Motorola, that today enjoys widespread application in many sectors of industry. Six Sigma seeks to improve the quality of process outputs by identifying and removing the causes of defects (errors) and variability in manufacturing and business processes (Wikipedia).

The five steps in Six Sigma (DMAIC)


The define phase identifies potential projects; evaluates projects; selects a project; defines a project (preferably using SMART framework) and sets up the project team

AT&T uses the Pareto Principle (Juran Principle) to choose project(s) calling it the Pareto Priority Index (PPI): PPI = (savings * probabilty of success) / (cost * years to completion)

Projects should deal with a chronic problem; be feasible, signfiicant, measurable and serve as a learning experience Project teams usually include 6-8 persons using a cross-functional approach


The measure phase identifies key product parameters and process characteristics and measures the current process capability. The steps are:

  1. Verify the need
  2. Document the process
  3. Process flow diagrams shows the sequence of steps including key process output variables (KPOVs) and key process input variables (KPIVs).
  4. Defects are non-fulfillment of intended use
  5. Sympoms are observable from a defect
  6. Theories are umproven assertion of reasons for existance of defects and symptoms
  7. Causes are the proven reasons for the existance of the defect
  8. Plan for data collection "In God We Trust, All Others Bring Data" (Deming)
  9. Formulation of Theories -
  10. Fishbone (Ishakawa)
  11. Validate the measurement system
  12. Measure the baseline performance
  13. Measure the process capability



The improve phase designs a remedy, prove its effectiveness and prepare for implementation


The control phase designs activities to hold the gains of improvement