The PDCA cycle: plan, do, check, act and how it differs from PDSA

Most businesses carry out three of the four steps of the PDCA cycle. They come up with a plan, put it into action and step in when results disappoint. The step in between, calmly looking at what actually happened and why, gets skipped or shrinks to ticking off a list. The next round then starts from the same assumptions as the last. The organisation goes round in circles, but it does not climb.

The cycle is designed to prevent exactly that. It turns every change into a small experiment, with an expectation written down beforehand and an honest comparison afterwards. What works becomes the new standard. What does not work still yields knowledge for the next round.

What is the PDCA cycle?

PDCA stands for plan, do, check, act. The four steps form a circle, because the last step is the starting point for the next round. You will also come across the names Deming cycle and Deming wheel.

From Shewhart to Deming: where the model comes from

The circle begins with Walter Shewhart, a statistician at Bell Laboratories. In his 1939 book he drew specification, production and inspection not as a straight line but as a circle: what inspection teaches you feeds back into the specification. The editor of that book was a young W. Edwards Deming.

Deming took the idea to Japan. At a 1950 seminar for the Union of Japanese Scientists and Engineers (JUSE), he presented a cycle of design, make, sell and redesign based on market research. The Japanese called it the Deming wheel. Japanese managers soon turned it into the four steps plan, do, check, act. Nobody has ever claimed authorship of that version. In 1985 Kaoru Ishikawa extended it, adding the setting of goals and methods to the planning phase and training to the execution phase.

Deming himself kept returning to Shewhart's original cycle. He reintroduced it in 1986, and in 1993 he called it the Shewhart cycle for learning and improvement. In a 1990 letter to Ronald Moen he wrote that it should be called PDSA, "not the corruption PDCA".

PDCA or PDSA: what is the difference?

It looks like a choice of words, but it goes to the heart of the matter. Check suggests verifying whether something went according to plan. Study asks you to understand why the outcome is what it is. That is why the Deming Institute frames the third step as study: learning, not inspecting.

In 1991 Moen, Nolan and Provost added something that makes such learning possible: a prediction in the plan step. If you write down beforehand what you expect, you can establish afterwards whether your understanding of the problem was right. Without a prediction, every outcome looks logical in hindsight. In 1994 Langley, Nolan and Nolan expanded the cycle into the Model for Improvement, which asks three questions up front:

• Aim: what are we trying to achieve?
• Measure: how will we know that a change is an improvement?
• Change: which change can we make that will lead to improvement?

In practice many organisations use the name PDCA and still work along PDSA lines. That is fine. What matters is that the third step amounts to more than ticking off actions.

The four steps in practice

1. 01

   Plan: start with the cause, not the solution

   Write the goal as a SMART goal, find the cause of the problem and choose one change. Note down what you expect it to deliver, and how and when you will measure that. For financial goals, the budget belongs in this step as well.

2. 02

   Do: start small

   Test the change in one department, one location or one product line first. A small trial is cheap, quick and easy to reverse. Record what happens, including things that were not in the plan.

3. 03

   Check: compare with your prediction and with others

   Set the outcome against the prediction. Where the two do not match, that is where the lesson lies. Compare with an outside view as well: how are similar businesses doing? The profit and cost benchmark shows whether an improvement brings you closer to your sector or lifts you above it.

4. 04

   Act: embed it or try again

   If it works, record the new way of working in a standard, a work instruction or the annual plan, and roll it out further. If it half works, adjust it and run another round. If it does not work, stop and put what you learned to use.

Worked example: less waste at a bakery with three shops

A craft bakery with three shops throws away too much bread at the end of the day. The owner suspects that each shop still orders on gut feeling, based on what sold last week. Rather than overhauling all three shops at once, he decides to look into it with a PDCA round.

Fictitious Firmfocus example.

Two things are worth noting. The prediction was only half right, and that is precisely what produced the most valuable lesson: Saturday. And the two other shops made it possible to see that the fall came from the new rule, not from the season.

PDCA at every level: from improvement project to annual cycle

The cycle works at any scale. A team can test a small improvement in a week. A management team runs the same loop with the annual plan: planning before the year starts, executing through the year, studying the figures every month and adjusting every quarter. That is why PDCA is the backbone of planning and control, and why the ISO standards for quality management are built on it.

Pitfalls

• Check turns into box-ticking: the question "was the action carried out?" replaces "did it work, and why?". In every meeting, ask about the effect first and only then about the actions.
• No prediction beforehand: in hindsight every outcome looks logical. Write down your expectation before you start.
• Rounds that are too big: a cycle that lasts a whole year teaches you one lesson a year. Break large changes down into small trials.
• Act as a blame game: punish a setback and from then on you will only see safe plans and flattering figures.
• Figures that arrive too late: a monthly report that is only ready halfway through the following month makes every correction slow. Make sure the books close quickly.

SMEs and large organisations

Want a second pair of eyes in the Act step? The Firmfocus Advisor works through possible causes and measures with you, using your plan and the figures for your sector.