Six Sigma Frameworks ... So Many Acronyms

I want to provide a little bit of clarity on three six sigma frameworks you'll come across if you're studying for your Greenbelt exam or if you're an LSS practitioner and could use a tune-up on these methods. It's a shame that the way we're trained to articulate these improvement frameworks is through acronyms and so I have to warn you that this post of full of alphabet soup. But if you stay with me, you'll learn about the frameworks of DMAIC, DAMDV, and IDOV and be a better communicator on these methods to the improvement teams you lead.

This is post is going to be in two main parts. First, you'll learn about improving existing processes. I'll talk about the plan-do-check-act cycle (PDCA) and how it's foundational to the primary six sigma improvement method of define-measure-analyze-improve-control (DMAIC). The second part will be about creating new processes through design for six sigma (DFSS). Here there are two frameworks: define-measure-analyze-design-verify (DAMDV) and identify-design-optimize-verify (IDOV). And as always, at the end of the post, I'll provide a few resources if you want to study further.

Improving existing processes

For six sigma, we typically problem solve for existing processes. The formal six sigma framework is DMAIC, but I want to start with a simpler concept: PDCA.

PDCA

The plan-do-check-act cycle (PDCA) isn't unique to six sigma. This is an improvement model that's applicable for any process. PDCA is also sometimes called PDSA for plan-do-study-act, and in the military the "OODA loop" (observe-orient-decide-act) is a version of PDCA.

I like PDCA because it's simple and cyclical. Once you complete the "act" step of the cycle, start over with a new process improvement plan.

Here are short definitions of each step:

  • Plan. You and your team determine the purpose and goals of the problem solving or improvement project. The best method in solving the problem is selected as well as understanding what data should be collected during the project.
  • Do. You and the team carry out the plan. Do it!
  • Check. During this phase, the results and the data from the "Do" step are evaluated against the goals the team determined.
  • Act. Also sometimes referred to "adjust,"  the team determines changes that need to be made to improve the process. With the information from the "Do" and "Check" steps, the team implements adjustments to the process that they are working on.

After once through PDCA, the team has better knowledge of the process problem and now they have a much better starting point for planning next improvement cycle.

I write PDCA first because it underpins the ideas behind six sigma's process improvement frameworks. It's most similar to six sigma's DMAIC improvement method.

DMAIC

DMAIC (pronounced da-may-ic) is the most common framework used in six sigma and is the focus of the Greenbelt exam. In fact, ASQ's study guide is organized according to each element of the DMAIC cycle. Each step of the cycle has a section of the study gudie dedicated to it.

DMAIC is best used for making continuous improvements for existing processes and products (versus massive redesigns - for new designs and redesigns, see the DFSS methods below). Examples of improvements in existing processes could be things like re-aligning to better meet customer needs or ensuring that quality standards are kept in processes and products.

Again, here are short definitions for each step:

  • Define. Identify the issue or problem to be solved, stakeholders, and relevant metrics. A project charter document captures these project characteristics.
  • Measure. Collect data about how the process is completed (i.e., how the work is done). A baseline is needed on the current state. Additionally, companies often do not have the right data and this may require more time for your project.
  • Analyze. Study the data collected to understand what is going on with the process. The level of analysis will vary depending on the scope of the problem being solved.
  • Improve. At this point in the cycle, the team has enough information to brainstorm solutions, select the best one, and implement changes to improve the process.
  • Control. The team creates a control plan which outlines how changes are properly implemented, who is responsible for what, and how improvements are kept.

Since DMAIC is a cycle, just like PDCA, repeat as necessary.

How does DMAIC relate to the PDCA?

Don't spend too much time trying to find a 1:1 relationship between the two frameworks. I spent entirely too much time trying to make an exact match the steps of the two processes together.

What you need to know are the big similarities. First, there's the planning stage we need to complete before doing anything. Second after planning, make the improvement or the "do" step. Third, look over the teams work; this is the check/control steps. Finally, both are cycles and, once an improvement cycle is complete, a culture of continuous process improvement tells us to restart the improvement cycle.

DFSS is for new design or redesign

When a problem requires designing a new process or a massive process redesign, improvement teams need to employ a framework from design for six sigma (DFSS). In researching for this post, I found a blog post titled "11 Known Design for Six Sigma Methodologies." Eleven. In one of my six sigma handbooks, you'll find:

"... other [acronyms] include DCOV (define, characterize, optimize, verify), ICOV (identify, characterize, optimize, validate), DMEDI (define, measure, explore, develop, implement), IDDOV (identify, define, develop, optimize, verify), and GD (good design, good discussion, good dissection." (Munro, Ramu, Zyrmiak. The Certified Six Sigma Greenbelt Handbook, Second Edition. ASQ Quality Press: n.d.)

What a rabbit hole to go down.  Why so many frameworks? I have no idea, and there isn't a good article that explains why (so this is probably a good topic for a future blog post). But what this does show is that there's no single accepted framework for DFSS. Contrast this to the DMAIC which is the main six sigma improvement method if you have an existing system.

Although these design processes have different acronyms, they are all essentially the same when you look at design for six sigma keeping PDCA in mind: plan the improvement up front, do something to improve, check your work, and then adjust based on what you and the team have learned. The main difference is that a DFSS is not a cycle. The end goal is to have implemented a new process (or drastically redesigned a process) so that the process achieves six sigma quality. Once the new process is in place, I argue that there's no need redesign it or create a new design again and this is why the illustrations below have a distinct beginning and an end.

Although there are up to eleven known DFSS frameworks, here are the two most common ones. They're both similar and it's more important to understand the main points in the paragraphs above.

DMADV

  • Define. Identify the primary design objectives.
  • Measure. Identify and measure the factors that are critical to quality (CTQ).
  • Analyze. Explore/study the design alternatives.
  • Design. Design the alternative selected.
  • Verify. Validate the design is acceptable for all stakeholders.

IDOV

  • Identify. Identify the customer and product requirements (i.e., identify the design objectives).
  • Design. Create a concept design through understanding risks, critical to quality (CTQ) requirements, and other analysis tools (the same as the measure and analyze steps in DMADV.)
  • Optimize. Adjust variables in the design to optimize the design (arguably, this is a step of the design process).
  • Validate. Test and validate the design for acceptance by all stakeholders (see verify step above).

So what?

Why go through the trouble of learning these different methods in six sigma if they are all the same thing? Frameworks provide the basic building blocks and how these fit together for the central idea. Each problem solving framework has a clear beginning to the process (identify), an element of study or analysis before getting to the actual problem solving, an element of doing, and then some form of checking the solution. And then the process is either a cycle (PDCA or DMAIC) or it's once through for a new design or redesign (DFSS). If you understand and distill these parts down to a very basic understanding, the chance of your team getting on board with you using one of these methods increases.

Being able to clearly communicate how to problem solve does two things for you as an LSS practitioner. First, it will help in preventing your team from jumping to a solution they think will work. This will occur if no one implements rigor into the problem solving process. Any of the methods in this post inject that rigor. Second, your perception as an expert increases through the clear communication. As an expert, you'll experience much more ease in people accepting your idea and moving forward on an improvement project.

Resources

So if you're interested in further studying these methods, here are a few resources you can glom onto to increase your expertise and the chances that you and your team find success in your improvement projects.

  • This is one of the better blog posts for DFSS.
  • The Certified Six Sigma Greenbelt Handbook, Second Edition. This is a must-have if you plan on taking ASQ's CSSGB exam. Amazon link
  • The ASQ Certified Six Sigma Study Guide (2017). I used this as my main study prep material for the Greenbelt exam. Amazon link
  • Lean Six Sigma for Dummies, Third Edition. I enjoy the "For Dummies" series. I think they do a great job of simplifying all sorts of topics and had a much best explanation of DMAIC vs. DMADV that I found. Amazon link

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