Framework library · Operations and resilience

Six Sigma DMAIC

DMAIC is the project cycle of Six Sigma: define the defect in the customer's terms, measure how often the process produces it, analyse why, improve the causes that matter and control the process so the gain holds. Each phase passes a tollgate on evidence before the next begins, and the result is stated as defects per million opportunities.

LevelIntermediate
TimeThree to six months for a typical project; an hour to set up the measures
Who to involveA project lead trained in the method, the owner of the process, and the people who run it every day.
Also calledDMAIC, Six Sigma, define, measure, analyse, improve, control, Lean Six Sigma, DPMO, sigma level

Use it when

  • A repeated process fails often enough to count, such as radio units failing final test, orders keyed wrongly or repeat engineer visits, and you want the failure rate down by a stated amount.
  • The cause of the defects is not known, and the fixes tried so far have been guesses.
  • You need a result finance will accept: a baseline, a target and a measured change on the same definitions.
  • A fix exists but keeps slipping back, and you need controls that hold it in place.

Avoid it when

  • The problem is delay and handoffs rather than defects. Start with value stream mapping or Lean.
  • There is too little volume to measure. A process that runs twenty times a year cannot show a defect rate. Use five whys or a fishbone diagram on each failure.
  • The answer is already known and only needs doing. Run it as an ordinary project rather than a five-phase study.
  • You are designing a new process or product. DMAIC improves what exists. Design thinking or a design method such as DMADV fits better.

How to run it

  1. Define the defect and the customer

    Write what counts as a defect from the customer's side, what one unit is (a radio, an order, a visit) and how many opportunities for a defect each unit has. Agree the scope and the target with the sponsor.

  2. Measure the baseline

    Count units, defects and opportunities over a representative period, and check that the measurement itself is reliable. The calculator turns the counts into defects per million opportunities (DPMO) and a sigma level.

  3. Analyse the causes with data

    Sort the defects by type, then test the likely causes against the data. Keep the two or three causes that explain most of the defects.

  4. Improve the causes that matter

    Change the process at the cause, pilot the change and measure again on the same definitions.

  5. Control the gain

    Hand the process owner a control plan: what is measured, how often, the limits, and what happens when a measure breaches them.

  6. Pass each tollgate on evidence

    At the end of each phase the sponsor reviews the evidence and decides to proceed, rework the phase or stop the project.

Work through it

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Mistakes to avoid

  • Changing the definition of a defect or an opportunity between baseline and result. The improvement then comes from the counting, not the process.
  • Inflating the opportunities per unit. Counting every screw as an opportunity makes DPMO small and the sigma level flattering.
  • Jumping to improve before the analysis is done. Fixes chosen before the data are in tend to treat the loudest cause, not the largest.
  • Closing the project without a control plan. Gains decay quickly when nobody owns the measure.

Where it comes from

Six Sigma was introduced at Motorola in 1986 by the engineer Bill Smith as a way of measuring and reducing defects, and spread to other large companies in the 1990s, most visibly after General Electric made it central to its strategy in 1995. DMAIC is the cycle Six Sigma projects follow to improve an existing process. The sigma level conventionally includes an allowance of 1.5 sigma for long-term drift. Source.

Six Sigma is a registered trademark of Motorola Trademark Holdings, LLC. This page describes the method independently and is not endorsed by Motorola.

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