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DMAIC v Six Sigma v Lean: Choosing a continuous improvement framework

Synonyms, semantics, subtle differences. The world of continuous improvement is littered with these, but whether it’s DMAIC, Six Sigma or Lean, there are logical phases in each approach to improvement. These are the questions you need to ask yourself, no matter the improvement framework.

Written by: Nigel Richardson


Today I would like to challenge your understanding of the differences between DMAIC, Lean and Six Sigma.

Not necessarily to be destructive, but more so because there is a set of logical phases to any improvement project, regardless of the framework applied.

In fact, this blog’s goal is to ensure the exam questions of each methodology are answered for each phase. 


Choosing your Continuous Improvement Path

In my experience these exam questions never change, even if the debate about the semantics of the phases continues.

The level of tools and rigor you apply is based on your judgement on rigor vs stakes vs urgency.


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DMAIC is a data-driven quality approach used in continuous improvement.

While it is a core part of Six Sigma, it can also be implemented alone.

DMAIC is an acronym for five stages:

  1. Define
  2. Measure
  3. Analyze
  4. Improve
  5. Control


In any case, these are the questions and tools you can apply as you run through a project using DMAIC.

Phase The exam question(s) The tool(s)
  1. Am I set up for success?
  2. Do I have approval to proceed?
  3. What is the business problem I am trying to solve?
  4. Why is it important to the business?
  5. What is the urgency?
  6. Who will I need on my team?
  7. Who is my sponsor, how will they help me?
  8. Who else will be impacted and who’s support do I need?
  9. What are the scope boundaries for my improvement (process, geography, function etc.)?
  10. Has anyone else previously addressed this problem that I can learn from?
  1. Project charter
  2. Stakeholder analysis
  3. Project plan
  4. SIPOC
  5. Historic data analysis (KPI baseline)
  6. Knowledge management review
  1. Do I understand the current state?
  2. Have I collected Voice of the Customer to understand the requirements that will drive our decision making?
  3. Do I have a baseline of performance so I can measure the effect of my improvement?
  4. Do I understand the processes involved and who supports them?
  5. Have I defined and quantified what is bad such as the wastes, variation or other undesirable effects?
  1. Data collection plan
  2. KPI tree
  3. Voice of the Customer (kano model, CTQ tree)
  4. Demand (profiles, product families, takt.)
  5. Process observation and mapping
  6. Data collection plan: operational definitions and measurement system analysis
  7. 8 wastes
  8. Descriptive statistics and data visualization (e.g. pareto, frequency distribution, means and standard deviations)
  1. Do I have clearly defined problem statements that summarize the priorities in the current state to fix?
  2. Can we articulate the root causes that need to be addressed and why they are the priority?
  3. Have I defined what I think the priority solutions needs to be?
  1. Problem statement
  2. Root cause problem solving (affinity diagram, 5 whys, fishbone)
  3. Solution specifications
  4. Solution definition and prioritization
  1. Have I designed the solutions required and developed the charters and plans for their implementation?
  2. Do I understand the potential risks to the solutions working and have mitigating actions in place?
  3. Have a drafted the relevant artefacts to ensure the changes will be sustained?
  4. Have those impacted by the changes been engaged in this work through communication and other project activity? 
  5. Is there a pull for this improvement?
  1. Project charter
  2. Process mapping (future state)
  3. Solution risk assessment e.g. FMEA (Failure mode effects analysis) and standard work (single point lesson)
  4. Impact of change assessment
  5. Stakeholder management plan and communications plan
  1. Have the new ways of working been adopted?
  2. Are people embracing the new ways of working?
  3. Have people stopped the old ways of working?
  4. Are we seeing the expected results?
  5. Has the change been sustained over time?
  6. What did we learn?  Has the project been shared with other related areas that may benefit from this improvement?
  1. Launch planning
  2. Sustainability criteria
  3. Updated process observation / confirmation content
  4. KPI reviews
  5. Post implementation review


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Six Sigma

Six Sigma is a statistical, data-driven approach to continuous improvement which focuses on eliminating defects in processes, services and product, process or service.

These are the questions and tools you can apply as you run through a project using Six Sigma as your framework.

Six Sigma term The exam question(s) The tool(s)

Process capability

Also known as: Cp and Cpk

Compares the “voice of the process” to the Voice of the Customer. 

The question is of how much variation sits within the customer specification limits. 

The more of the variability that sits within the limits to better the process capability.



Also known as: Defects per million opportunities

An alternate representation of process capability. 

Based on the current process capability, how many defects per million would be produced?


Measurement system analysis

Also known as: MSA

Evaluating your measurement system against its:

  1. Accuracy (to the true value)
  2. Repeatability (over time)
  3. Reproducibility (consistency across different systems or appraisers)

It is important to understand how robust the measures are behind the measurement system of the key KPIs you are trying to improve.

Sometimes you will need a round of improvement on how your information is collected.


Lean Management

In any improvement project you undertake, once you are clear on your current state and the problems you need to solve appear, you will quickly start to identify opportunities to apply some of these predefined Lean interventions and principles. 

Below is an overview of some of the more frequently applied contents of the Lean toolbox, I have included an explanation of a couple of terms from this tool box that I also mentioned above.

Lean intervention Summary When it should be applied


Also known as: Sort, Set in Order, Shine, Standardize, Sustain.

A comprehensive approach to workplace management comprising of the activities of Sort, Set in Order, Shine, Standardize, Sustain.

Where you have root causes for waste concerned with the quality of the working area with issues such as excessive movement or missing kit / tools.

5S is also a very empowering exercise to facilitate in an area. 

It is very tangible and serves as a great first step if you are working with an area for a period of time.

The visual workplace A basic principle of the work environment visually reinforcing the desired ways of working and standards with any deviations obvious at a glance.

Visual display – abnormalities stand out, performance can be understood at a glance. status boards, shadow boards, andon lights.

Visual controls – clear visual communication of instructions (e.g. traffic lights).


A mechanism of simple signals that regulate the flow of product in a pull production system.

Often a Kanban board is used for planning work and tracking delivery.

As part of an effort to reduce inventory, working capital and spend up the time taken to produce product in a waste free way.

Kanban’s as a method for work management is a key facet of Agile software development and many other forms of delivery in the present day.


A German word meaning rhythm or time. 

It is a way of converting demand into an expected per unit processing rate.

Remember Takt is a Voice of the Customer measure – it represents the demand required not the performance that can be done.

This can be used when you are designing processes that support fulfilling a product of a service without bottle necks.
Product families A way of segmenting your demand based on different clusters of process that are applied. This can be used to define your value streams.
Demand profiles

Segmenting your demand into 3 categories:

  1. Runners
  2. Repeaters
  3. Strangers 

This is based on their volume and variability.

Theory of constraints and Pacemaker The rate of a process must be synchronized across all processes and to the expected rate of demand (Takt).  

Mistake proofing


Designing a process with supporting, visualization or technology, that makes it impossible to get wrong (or extremely difficult). 

Consider a plug as a mistake proofed method of connecting your appliance with mains electricity.

Designing pick lists on a website.

Designing templates for staff to follow.

Marking out lanes in colored tape for customers to walk along.


Also known as: single minute exchange of dies

Historically applied to reduce manufacturing down time due to change overs. 

The principle is how to minimize the down time through maximizing the amount of activity that can be performed outside of that critical window during preparation.

Consider how motor sport pit stop times have reduced over the last 30 years to minimize the disruption to the cars flow around the track.

Understanding what work can be moved or modified to reduce this critical window of elapsed time.

IT maintenance windows.

Supply chain down time.

Whilst an overriding principle and approach and translating as 'change for better'. 

Kaizen is often referred to as an intensive workshop where problems are solved rapidly and change is implemented there and then.

Consider packaging some of the larger chunks of change into Kaizen style workshops. 

Fast track from problem statement to implemented solutions within a weeks intensive workshops.


Closing thoughts

This improvement framework overview has sought to deliver clarity in a world of information which can often lead to confusion over the steps, phases and tools to apply for the DMAIC, Six Sigma and Lean methodologies.

Regardless of the framework chosen for your improvement projects, I hope that it provides you with a handy checklist and cheat sheet for navigating through the tools available to you.


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About the author

Nigel Richardson is a continuous improvement expert. His background spans 20 years in business transformation and continuous improvement across retail, pharma, aviation and IT supply chain. He is passionate about supporting organizations to achieve their strategic, transformational and improvement goals, and outperform their peers year after year.

If you’d like to talk more about your strategic challenges, reach out to him on nigel.richardson@i-nexus.com or connect with Nigel on LinkedIn for the latest Strategy Execution insights.