What is DMAIC?
DMAIC (Define, Measure, Analyze, Improve, Control) is the problem-solving roadmap of Six Sigma. It is used for chronic, complex problems where the cause is not known and has to be found with data. Each phase ends with a tollgate review: the project sponsor checks the deliverables and decides whether the team moves on, loops back or stops.
The five DMAIC phases
| Phase | Purpose | Typical deliverables and tools |
|---|---|---|
| Define | Agree the problem, goal and scope | Project charter, SIPOC, voice of the customer, CTQs |
| Measure | Quantify the current performance | Data collection plan, Gage R&R, baseline sigma or capability |
| Analyze | Find and prove the root causes | Fishbone, Pareto, hypothesis tests, regression |
| Improve | Remove the causes and prove the effect | DOE, solution selection, FMEA, pilot |
| Control | Hold the gain | Control plan, SOPs and training, control charts, handover |
Sigma level and DPMO
The sigma level expresses defect performance on a common scale. Count the opportunities for a defect in each unit (for a form, the number of fields that can be wrong), then calculate defects per million opportunities:
DPMO = defects ÷ (units × opportunities per unit) × 1,000,000
The sigma level is the z-value of the yield plus the 1.5 sigma shift used by convention for long-term drift. 66,807 DPMO is 3 sigma, 6,210 DPMO is 4 sigma, 233 DPMO is 5 sigma and 3.4 DPMO is 6 sigma. Compare the baseline with the result after improvement to show the size of the gain.
DMAIC example
The example project reduces errors in packaging batch records. Define: 18 errors per 100 records delay batch release and cost about $180,000 a year; the goal is 5 per 100. Measure: with 40 entry fields per record, 312 errors in 1,720 records is 4,535 DPMO, or 4.1 sigma, and QA reviewers agree on 94% of errors. Analyze: three fields cause 71% of errors and the night shift has 2.3 times the error rate. Improve: redesigned pages piloted on one line bring errors down to 6.5 per 100 (4.4 sigma). Control is still to come: roll-out, training, a weekly chart and validated savings.
When to use DMAIC (and when not to)
- Use DMAIC for recurring, costly problems with unknown causes and available data.
- Use a PDCA or kaizen event when the solution is fairly clear and needs to be tested quickly.
- Use an 8D for a customer complaint that needs containment and a formal report.
- Use an A3 to tell the story of a problem on one page for leadership.
How to use this DMAIC tool
- Write the charter. Name the project, champion and leader. In the Define phase, write the problem, goal, business case and scope, and set the CTQ metric.
- Measure the baseline. Enter defects, units and opportunities to get the baseline DPMO and sigma level.
- Work through the phases. Click each phase to record its key findings, status and tollgate dates. Tick the tollgate deliverables as they are completed.
- Verify the improvement. Enter the current CTQ value and the after-improvement defect data to see the improvement and new sigma level.
- Plan the actions. List the actions with owners and due dates. Overdue phases and actions are flagged.
- Export. Export the project storyboard to PDF for tollgate reviews, or to Excel.
Frequently asked questions
What does DMAIC stand for?
DMAIC stands for Define, Measure, Analyze, Improve and Control, the five phases of a Six Sigma improvement project. Define the problem and goal, Measure current performance, Analyze the data to find the root causes, Improve the process by removing them, and Control the new process so the gain lasts.
What is a tollgate in DMAIC?
A tollgate is a review at the end of each phase where the champion checks the deliverables before the team moves on. For example, the Measure tollgate confirms the measurement system is reliable and the baseline is known. The tool lists the typical deliverables for each tollgate as a checklist.
How is the sigma level calculated?
Defects per million opportunities (DPMO) = defects ÷ (units × opportunities per unit) × 1,000,000. The sigma level is the standard normal value for the yield (1 − DPMO/1,000,000) plus the conventional 1.5 sigma shift. For example, 4,535 DPMO is about 4.1 sigma and 3.4 DPMO is 6 sigma.
What is the difference between DMAIC and DMADV?
DMAIC improves an existing process. DMADV (Define, Measure, Analyze, Design, Verify), also called Design for Six Sigma, is used to design a new product or process, or to redesign one that cannot be fixed by improvement.
How long does a DMAIC project take?
A typical Green Belt or Black Belt project takes three to six months. Simple problems with an obvious cause do not need DMAIC; use a PDCA, A3 or kaizen event instead.
Is DMAIC the same as PDCA?
DMAIC is a more detailed and data-driven version of the PDCA cycle. Define, Measure and Analyze correspond to Plan, Improve covers Do and Check, and Control is Act.