What
Six Sigma aims to reduce defects to 3.4 per million by eliminating variance through the DMAIC cycle. The five phases are: (1) Define — what is the problem? what is the target state? who is affected? (2) Measure — collect baseline data. No guessing, no anecdote. (3) Analyze — find root cause using fishbone, 5-whys, or Pareto analysis. Do not fix symptoms. (4) Improve — implement targeted solution. Pilot first, measure impact. (5) Control — lock in the gain. Add monitoring and set triggers to catch regression.
The key rule: never skip Measure — improving an unmeasured process is theater. In code, DMAIC maps to: define acceptance criteria → measure test coverage → analyze failure modes → improve code → add CI gates.
When to Use
Apply DMAIC when improving a process, reducing error rates, or addressing quality issues. Use it whenever you need a data-driven approach to process improvement rather than intuition-based changes.
How
- Define the problem, target state, and affected parties.
- Measure baseline data objectively.
- Analyze root causes using fishbone, 5-whys, or Pareto.
- Improve with a targeted solution — pilot first, measure impact.
- Control: lock in gains with monitoring and regression guards.
- Never skip Measure — improving an unmeasured process is theater.