What is Deming Cycle or Shewhart Cycle or PDCA?

8 mins read

You’ve worked hard to make your product, and the worst thing that can happen to your manufactured products is that it is defective. Unfortunately, if it’s not recyclable, all the money that you spent to make that piece is wasted. And even if it’s recyclable, you’ll still lose some percent of the money. Being co-founder of your company, you need to ensure that your product and process need to have as high accuracy as possible of being not defective. So how do you ensure that your products and process are defect free? Of course, it can never happen. Nothing is cent percent perfect. The only thing you can do is to push the chances of being non-defective to as much near as possible of 100%.

In Brief

When it comes to Problem Solving or Continuous Improvement of Process or Product, the first method that comes to our mind is Deming Cycle. It is an iterative four-step management process that is more like a cycle and comes back to the first step as soon as the fourth step gets completed.

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PDCA consists of four steps:

PDCA Cycle

It is also known as Deming Circle, Deming Wheel, Shewhart Cycle, Control Circle, Control Cycle, Plan–Do-Study–Act (PDSA), Deming Quality Wheel, and Deming Management Wheel.

Background of Plan-Do-Check-Act

Walter Shewhart


In 1924, Walter A. Shewhart prepared a one-page memorandum to effectively increase the quality of the products and forwarded to his manager. About one-third of that page was covered with a simple diagram of a cycle. He might have had not known that he had invented probably the best process to continuously improve a product or process. What he suggested was, after launching the pilot product, firstly, we need to first plan the improvements for next release. Secondly, do the implementation. Thirdly, check whether the newly added changes are performing as expected. Fourthly, if the changes are successful, we need to document it, and if it’s not, learn from the mistakes and again move to step one.

William Edwards Deming


In 1950, W. Edwards Deming, further improved the process by adjusting it a little. He modified the PDCA cycle to PDSA where “Check” is replaced with “Study” (and yes, it makes more sense). The fundamental idea of the process remains the same. The alteration of the third step to “Study” has made this cycle even more effective. Rather than checking whether the newly added changes are performing as expected, we now study its performance. Though all those changes, people are still more comfortable to call it as PDCA.

How to Use Plan-Do-Check-Act?

To keep this article from being boring and uninteresting, I am going to explain the four steps with an example of launching an iOS app. I chose this as an example because mobile app industry is booming, and more and more people are choosing this as a business. Let’s say that you are building an app that automatically schedules your content for social media. You probably want to tweet something to your targeted audience at the time when they’re up. So if you’re targeting customers in Japan and you live in US, you don’t have to be up till 3 AM to tweet. You can schedule it in your app, and it’ll automatically post at 3 AM US time. It’s a win-win case for you as well as your targeted audience in Japan.

Let’s begin the steps

1: Plan

If you remember the above cycle, the first step is Plan. After launching your pilot product, the very first thing you need to do is plan the things that you’ll be rolling out in next version of your product. It might be new features or some improvements. The best part is that it works even when you don’t have any pilot product. If you’re working on your prototype, you can still follow this cycle. The only thing that you’ll miss is the experience and data that you would have if you had launched your product.

Your app currently supports only Twitter for scheduling. Now suppose you want to add this functionality for Facebook as well. Now it’s time to plan the things for your next release. What are the additional features required for Facebook, does Facebook support automatic scheduling, what are Facebook APIs etc.?

After brainstorming the features that you’d like to launch in your next version, the next thing you need to do is to brainstorm how best can they be done. How can I make my app as much fast as possible, how can I make it bug-free etc.? It’s better to create a sheet of features that you’re going to release so that you can check their performance in the third step.

It’s good to create a wireframe for your next release.

2: Do

It’s time to implement the changes that you planned in the previous step. As you need to modify your app that supports Facebook also, you need technical skills here. Either you have an employee to make those changes, you already have that skill, or you’re going to outsource this task to someone and prepare a contract.

This step in itself is a small PDCA. You implement the changes, found a bug, and fix it. You have implemented the new feature in your app for Facebook, and found that the app crashes whenever you schedule the content that’s going to post after 3 days from today. Now you need a check the root cause, analyze, and plan to fix this bug. After that, you need to fix this bug. Doesn’t it look like a PDCA?

3: Check

The newly implemented features need to be tested here. This step is probably the least time-consuming and takes 1 day to 1 week.

You need to test your app in every aspect. Be it speed, look, features, CPU utilization, optimization, all these have to be tested. Any flaw in them can result in a catastrophic fail. The competition outside is vast, and you need to have a nearly perfect app to stand a chance against big players.

The sheet we created in the first step may come handy here to analyze the performance of every new feature.  It’s also better if you test the performance of the features that you had already rolled out, and make sure that the newly added features aren’t killing the old features by anyway.

4: Act/Adjust

This is the most crucial step among all four. The reason being that is that it provides you the data. This is where the true entrepreneurship in you comes into the picture as you need to make decisions based on this data. The data that you have, needs to be analyzed to launch the next version of your app.

If the change is successful, let’s roll it out to customers. Time to analyze how much your customers are liking your app.

The best way to check is the review that your app is receiving. Your customers are honest and they’re giving you 5 stars or 1 star for a reason. Make sure that you read their comments as well. It’ll be also good if you implement a feedback feature in your app, kind of support, where your customers can share the things they’re liking, not liking, or probably want to have in next release.


Now repeat it again and again. Make your app as much perfect as possible. Integrate more features, make it as much optimized as possible, make it faster, make is less battery consuming. The possibilities are never-ending. You need to hunt for those by the data that you have received in the fourth step.

When to Use Plan-Do-Check-Act?

Now there comes a question. When should we use Plan-Do-Check-Act or Deming Cycle?

  • When you want to continuously improve a product or process
  • When rolling out next version of your product
  • When developing a new or improved design of a process, product or service
  • When creating a new process that’s repetitive
  • When you’re planning to have as much as data as you can have to analyze in order to verify and prioritize the solution to problems

Limitations of Plan-Do-Act-Check

As mentioned earlier, nothing is perfect, neither does Plan-Do-Act-Check. There are many factors that contribute to the success of a product, and Deming Cycle doesn’t include all of them. Few of them are listed below.

  • Every single task, or at least most of the tasks will be done by humans. It does not include human side like skills, motivation etc.
  • It does not tell how to effectively communicate with your developers or engineers.
  • It tells you that you need to continually improve your product by following a cycle, but does not tell you how.
  • Apart from knowing this cycle, you need to have a good knowledge other aspects as well that your business is involved in.
  • For big organizations, implementing this cycle is a cumbersome task and you need to spend a lot to train all managers, buy equipment, create documentation etc. You need to make sure that the return outweighs the money you spent to implement this method

I hope that you have enjoyed this tutorial. Don’t forget to share it with your friends and family using the buttons on your left side.

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