PDCA (Plan Do Check Act) vs. DMAIC (Define Measure Analyze Improve Control)



Although only 30 years old, I tend to lean my quality styles to the old tried and true methods. I track continual improvement issues under a PDCA format. A management group recently observed this report. They (management) are caught up in the six sigma buzz, requested that I report on issues in the DMAIC format.

What's the fundamental difference? Are both not methods of continual improvement? Or are the deep philosophical differences between the two? Is one more appropriate under a certain set of conditions than the other?

Help me understand the differences. :confused:


Fully vaccinated are you?
I found this - I'll leave the explaining to the experts... In my eyes, they're the same thing with different labels.


As far as the PDCA, see *** DEAD LINK REMOVED *** for some details.


The concept of the PDCA Cycle was originally developed by Walter Shewhart, the pioneering statistician who developed statistical process control in the Bell Laboratories in the US during the 1930's. It is often referred to as `the Shewhart Cycle'. It was taken up and promoted very effectively from the 1950s on by the famous Quality Management authority, W. Edwards Deming, and is consequently known by many as `the Deming Wheel'.

Plan to improve your operations first by finding out what things are going wrong (that is identify the problems faced), and come up with ideas for solving these problems.

Do changes designed to solve the problems on a small or experimental scale first. This minimises disruption to routine activity while testing whether the changes will work or not.

Check whether the small scale or experimental changes are achieving the desired result or not. Also, continuously Check nominated key activities (regardless of any experimentation going on) to ensure that you know what the quality of the output is at all times to identify any new problems when they crop up.

Act to implement changes on a larger scale if the experiment is successful. This means making the changes a routine part of your activity. Also Act to involve other persons (other departments, suppliers, or customers) affected by the changes and whose cooperation you need to implement them on a larger scale, or those who may simply benefit from what you have learned (you may, of course, already have involved these people in the Do or trial stage).

Al Dyer

Maybe an opinion that will be shot down,

6S is nothing more than process improvement. Many companies are investing alot of maney to prove they are 6s when there are already similar processes that have been around for years. One I like is Ford's Q.O.S..

Why spend extra money when we should all be doing this in the first place, process measurables and result measurables provide the data needed for any company to assess their standing and needs.

Now waiting for the fallout, although it won't change my mind.

Alan Greatbatch

I have been working with TQM since the late eighties and PDCA has always been at the heart of the philosophy. From this philosophy the company I worked with at the time expanded the PDCA cycle to an 8 step process for problem solving and continuous improvement but never lost it roots from the Deming Cycle. It was defined as:

1. Define the Problem
2. Implement/Verify Interim Action¨
3. Aquire and Analyse Data
4. Determine Root Cause(s)
5. Evaluate Possible Solutions

6. Implement

7. Verify the Results

8. Standardise and Future Actions

This approach seems to tie PDCA and DMAIC together quite nicely.

I have been using this system very succesfully for nearly 15 years in 6 different companies and in 3 different European countries.

I am a naturally lazy guy so I am always on the look out for tools that makes my job easier. I have never seen an easier tool that can incorporate all other tools, I have never been shown a better approach and I have never found anyone one to criticise it. Also customers love it as a Corrective Action Report. Just ensure that Step 1 is weakness focused, succinct and does not suggest a cause.

More info available if required.





Since 1998 we are training Six Sigma Green/Black Belts through the PDCA cycle. Definitely there are no differences between them.

Whirlpool of Brazil, Johnsonn & Johnsonn of Brazil, International Motors of Brazil and a great number of firms have their personnel trained with us through the PDCA cycle. All our products are "PDCA based", including "Six Sigma Black Belts".

Perhaps a little more time is needed for the business world to fully understand that there are no differences between them.

Cristián Carranza
Senior Consultant
Fundação de Desenvolvimento Gerencial - Brazil


Change Agent and Data Storyteller
Super Moderator
PDCA I understand...it is a well-established methodology within my organization.

DMAIC I know little about, but looking at what it stands for, I'm seeing the following associations:

Define = Plan
Measure = Do
Analyze = Check
Improve = Act
Control = ????

I have said before that there can be no improvement without standardization. Is that what the Control equates to, then?...an established process/practice?
There you go...You got it!

The Control part is institutionalizing the change. In my book, this is the Act part. Once you have Checked and made sure that the Do that you Planned is an actual improvement, then you Act to make the change standard and controlled.

In Six Sigma methodology, this includes a continuing analysis of the Change via Dashboard metrics, etc. to make sure that the change stays stable.

Paraphrased from Six Sigma for Managers, Greg Blue
Consider Y = some function of X
Define = Identify important problems in your processes.
Measure = Select Critical to Quality (CTQ) characteristics in the product or process, define performance standards, validate measurement system, establish process capability (Y)
Analyze = Define improvement objectives, identify variation sources, screen potential causes for change (Y) and identify vital fiew (X)
Improve = Discover variable relationships among vital few, extablish operating tolerances, validate measurement system (X)
Control = Determine ability to control vital few, implement process control system on vital few (X)

Steve Prevette

Deming Disciple
Super Moderator
Marc said:
Just wondering if anyone has anything to add to this...

I should point out that Dr. Deming and others got away from "Check" and use "Study" instead. Thus, PDSA cycle. This change is what differentiates DMAIC vs. PDSA. In "study" we study the results, non-judgementally. We see if an improvement occurred, preferably using SPC. We should NOT compare against some numerical goal that was established back in the Measure stage, as the six sigma folks would tend to do. Then we do the final "Act"

I think the weakness of DMAIC is that final "C" for control. That implies to me more of an endpoint to the process. PDSA is definitely intended to move from the Act stage back to Plan to see if anything further can be done on the next cycle.

Another difference is that the "Do" in PDSA is a small scale prototype. DMAIC just moves straight into "implementation" after measuring and analyzing.


Great stuff!!!

Nothing in Quality is ever new. I wrote my first ISO 9001:1994 manual using a 1962 Quality Manual for refrence.
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