The Shewhart cycle (also referred to as the Deming Cycle, or the Deming Wheel, after W. Edwards Deming) was named for Walter Shewhart, who discussed the concept in his Statistical Method from the Viewpoint of Quality Control book. It is the continuous improvement cycle of Plan, Do, Check, Act (PDCA).

Although Walter A. Shewhart first discussed the concept of PDCA in his book, published in 1939, it was Deming who encouraged a systematic approach to problem solving and promoted the now widely recognised four step process for continual improvement.

Deming refers to it as the PDSA Cycle (Plan Do Study Act). The Japanese call it the Deming Cycle. Others call it the PDCA Cycle (Plan Do Check Act) or the Deming Wheel.

The model can be used for the ongoing improvement of almost anything and it contains the following four continuous steps: Plan, Do, Check(Study) and Act.

The Shewhart Cycle

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).

The FOCUS - PDCA Methodology

Some people expand PDCA to a nine-step process that incorporates a FOCUS stage before the PDCA cycle. These nine steps are:

1. Find a process that needs improvement.
2. Organize a team that knows the process.
3. Clarify knowledge of the process by flowcharting or data collection.
4. Uncover the underlying causes of variation or poor quality.
5. Start the P-D-C-A cycle by choosing a single modification to the process.
6. Plan a pilot to test the improvement.
7. Do the improvement.
8. Check that the process actually improved.
9. Act to adopt, adjust or abandon the change.

The Joiner Seven Step Method

The Plan-Do-Check-Act cycle can (and should) be applied at all levels of improvement. However, it is useful to have a fuller, more detailed macro P-D-C-A that applies to the project as a whole. This provides us with:

• a framework with which we can visualize progress through a project,
• check-steps that allow us to see that we are not trying to proceed too quickly through part of the improvement process without having gained sufficient understanding,
• a means of documenting a project.

One useful framework to do this is the "7 Step Model", developed by Joiner Associates (Brian L. Joiner). As well as providing a disciplined framework for progressing through a project, the 7 Step model provides a good framework for documenting a project. The 7 Steps are:

STEP 1 Define Project Purpose and Scope

• Focus on strategically important problems
• Choose an appropriate project team and team leader
• Clarify the project mission
• Determine how much progress can be expected
• Formulate a framework and execution plan for the project

STEP 2 Current Situation

• Understand the present process
• Determine customer needs and expectations
• Flow chart the process
• Collect data to identify the real problem
• Standardize the process, if necessary

STEP 3 Cause Analysis

• Dig down for the root causes of the problem
• Identify the major potential causes
• Verify them with data, if possible

STEP 4 Solutions

• Choose between alternative solutions
• Keep solutions simple
• Identify barriers to implementing solutions
• Plan and make necessary changes (use PDCA)

STEP 5 Results

• Evaluate the solutions
• Collect data, to compare before and after improvement
• Compare results with what we expected

STEP 6 Standardization

• Standardize the new process
• Document the changes made
• Error proof the process

STEP 7 Future Plans

• Review what has been learned from this project
• Decide whether to continue with this project, or
• Close project, and move on to a more pressing project.

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