Key facts
- Purpose: give a team a repeatable route from a process problem to a proven, standardised fix.
- Two families: lean methods remove waste and delay; Six Sigma methods reduce variation and defects. Lean Six Sigma combines them.
- Most are cycles: nearly all follow plan, test, check and standardise, so they share more than their names suggest.
What are the main process improvement methodologies?
| Methodology | What it does | Best for |
|---|---|---|
| Lean | Removes the 8 wastes and improves flow | Slow, wasteful, multi-step processes |
| Six Sigma | Uses data to cut variation and defects | Quality problems with an unknown cause |
| DMAIC | Define, measure, analyse, improve, control | Complex problems that need statistical proof |
| PDCA | Plan, do, check, act, repeated in small loops | Everyday fixes the team can trial in days |
| Kaizen | Small, frequent changes by the people doing the work | Building a daily improvement habit |
| A3 | Tells the whole problem on one page, with leader coaching | Problems that take weeks and need alignment |
| Theory of constraints | Finds and relieves the one step limiting output | Throughput limited by a bottleneck |
How do you choose a process improvement methodology?
Start with the problem, not the method.
- Is the cause obvious and local? Use PDCA or kaizen and trial the fix this week.
- Is the process slow or crossing departments? Map it with value stream mapping and apply lean.
- Do results vary with no clear reason? Use DMAIC, because the data has to prove the cause.
- Is one step holding up everything? Apply the theory of constraints to that step first.
- Does it need sign-off from several leaders? Write it as an A3.
Lean vs Six Sigma: what is the difference?
Lean asks "where is the waste?" and attacks delay, rework and handovers. Six Sigma asks "why does the result vary?" and attacks the spread of outcomes. Many sites use both, with lean for flow and DMAIC for the hard quality problems.
Do you need to pick just one?
No. Methodologies work as a toolkit. A daily kaizen habit sits underneath, PDCA runs each trial, and larger problems escalate to A3 or DMAIC. What matters is that each improvement ends in updated standard work, so the gain holds.