The PDCA Cycle is a checklist of the four stages which you must go through to get from `problem-faced' to `problem solved'. The four stages are Plan-Do-Check-Act, and they are carried out in the cycle illustrated below.

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'.

Use the PDCA Cycle to coordinate your continuous improvement efforts. It both emphasises and demonstrates that improvement programs must start with careful planning, must result in effective action, and must move on again to careful planning in a continuous cycle.

Also use the PDCA Cycle diagram in team meetings to take stock of what stage improvement initiatives are at, and to choose the appropriate tools to see each stage through to successful completion.
How to use the PDCA Cycle diagram to choose the appropriate tool is explained in detail in the `How to use it' section below.

Plan-Do-Check-Act

Here is what you do for each stage of the Cycle:

• 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).

You have now completed the cycle to arrive at `problem solved'. Go back to the Plan stage to identify the next `problem faced'.

If the experiment was not successful, skip the Act stage and go back to the Plan stage to come up with some new ideas for solving the problem and go through the cycle again. Plan-Do-Check-Act describes the overall stages of improvement activity, but how is each stage carried out? This is where other specific quality management, or continuous improvement, tools and techniques come into play. The diagram below lists the tools and techniques which can be used to complete each stage of the PDCA Cycle.

Click on the image to see a full-size version

This classification of tools into sections of the PDCA Cycle is not meant to be strictly applied, but it is a useful prompt to help you choose what to do at each critical stage of your improvement efforts.

Other references

Many authors have written about the PDCA Cycle or variations of it. For a sample of the different approaches see the books listed below.

`Out of the Crisis', W Edwards Deming, MIT 1989

`Kaizen', Masaaki Imai, McGraw-Hill, 1986

`The Team Handbook', Peter R. Scholtes, Joiner Assoc, 1988