What is the Deming Cycle?


A quality management system (QMS) is a collection of business processes as well as technical processes focused on consistently meeting customer requirements as well as regulatory and legal requirements. It is aligned with an organization’s purpose and strategic direction. Quality Management System requirements include a commitment to continuously improve and this commitment is made by management in the Quality Policy. The Deming cycle is an important tool for use by organizations to continuously improve processes and ultimately improve the Quality Management System.

What is the Deming cycle?

Also known as the PDCA cycle, the Deming cycle is a continuous improvement and problem solving model made up of 4-steps:

P-LAN: Design or revise the process components to improve results

D-O: Implement the plan and measure its performance on a small scale

C-HECK: Assess the measurements and identify their meaning

A-CT: Decide on changes needed to improve the process

In the 1950s quality guru Edward Deming proposed that business processes should be analyzed and measured to identify sources of variations that cause products to deviate from customer requirements. He adapted the Shewart cycle which was first described by Walter Shewart in the 1920s and it became popularly known as the Deming cycle. This tool has since been adapted for and used in various organizations and various processes including healthcare and laboratory operations.

The Cyclic nature of the Deming Cycle/PDCA cycle

The Deming Cycle is called a ‘cycle’ because the 4-steps are repeated over and over, bringing incremental improvement each time, and large improvements over time.

The simple diagram below illustrates this:

The Deming cycle

The Deming cycle can be used to solve problems in any process by carrying out a planned improvement project, which, if successful can then be implemented on a wider scale.


This stage involves, analyzing the process that needs to be improved and/ or pinpointing the causes of the problem that needs to be solved.

First of all the problem as to be defined.

It is important to have data to show the magnitude of the problem, where possible, e.g.

Patients are spending 2 hours on average in the laboratory from reception to blood collection, a waiting time of 1 hour is more acceptable. Since the long waiting time means customer satisfaction this process needs to be analyzed and improved. You may have started receiving complaints from patients, or you may just realize that the process needs to be improved.

Problem-solving tools like the 5 Why’s and the Fishborne analysis can be utilized to find the root cause of the problem. In some situations, there may be many issues contributing to the problem. Mapping the processes involved in the operation under investigation is useful in identifying what changes can be made and at which point.

The PDCA cycle ensures that changes are effected methodically and each action can be linked to the change.

The plan involves exactly what will be done, how often, and who is responsible for each task. The project is done on a small scale, it should be clear for how long this will be done.

DO: Implement the plan and measure its performance

At this stage, the plan is put into action and the plan has to be followed as closely as possible. In the example given above, you may start with implementing changes only on selected days for the defined period. The full implementation will be done once the project is successful. This serves to save the company money and time implementing organization-wide what may not bring about the desired results. Deming cycle, Do stage

It is critical to measure what effect the changes being implemented are having, at determined intervals. It should be clear what is being measured so that results can be directly linked to the appropriate changes. The interval of measurement should be short so that any trends can be detected and suitable changes effected. Do not worry so much about analyzing the data at this point.

Remember to collect as many data as possible and to document, document, document!


CHECK: Assess the measurements and report the results to decision-makers

Also, known as the Study phase, this is a data analysis stage; graphs, charts, pie charts etc are useful to show the results of the effected changes. Deming preferred the term study I.e study the result, measure effectiveness, and decide whether the hypothesis is supported or not. Excel is a most useful tool in this stage of the PDCA cycle.Deming cycle, Check stage

The collected information is analyzed at the end of the defined period so that any results obtained are not sporadic but can be confirmed to be a result of the changes. If the project is working, positive changes will be seen e.g a decrease in the proportion of unsuitable samples, an increase in the number of customers, a decrease in the proportion of defective products, a decrease in patient waiting times etc

ACT: Decide on changes needed to improve the process

Now we act on the results from the check stage. If there is no significant change or there is a negative change, its time to start over, which means going back to the planning stage and making a different plan, consider why this project failed and what should be done differently.
A positive change means the changes can now be implemented on a larger scale. The advantage of this is knowing for sure that the changes will bring about the desired changes. Management, therefore, is willing to finance the effecting of the changes because there is evidence to support that it does work.

However, it does not stop here, the organization should continue to go back and plan and continuously improve processes, as no process and indeed no system can ever be perfect, there is always room for improvement.


Most businesses want to improve, however making the necessary changes is not always easy. The Deming Cycle is one of the cornerstones of a Quality Management System that helps organizations of any type and industry break out of stagnancy and transition to a system of continuous improvement.

If you want to use the Deming Cycle to improve processes within your organization and are still not sure how to do this, leave me a message below and I will be sure to get back to you. Have fun improving your processes.

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