•The Deming cycle, or PDSA cycle, is a continuous quality improvement model consisting of a logical sequence of four repetitive steps for continuous improvement and learning: Plan, Do, Study (Check) and Act.

• The PDCA cycle is also known as the Deming Cycle, or as the Deming Wheel or as the Continuous Improvement Spiral.

•W. Edwards Deming in the 1950's proposed that business processes should be analyzed and measured to identify sources of variations that cause products to deviate from customer requirements.

•He recommended that business processes be placed in a continuous feedback loop so that managers can identify and change the parts of the process that need improvements.

•The PDCA cycle was in fact originally developed by Walter A. Shewhart, a Bell Laboratories scientist who was Deming's friend and mentor, and the developer of Statistical Process Control (SPC) in the late 1920s.  So sometimes this is referred to as the "Shewhart Cycle".  There are also several recent variations on this concept.

The Plan stage is where it all begins. It is where you design or revise business process components to improve results. Prior to implementing a change you must understand both the nature of your current problem and how your process failed to meet a customer requirement.

The Do stage is the implementation of the change. Identify the people affected by the change and inform them that you’re adapting their process due to customer complaints, multiple failures, continual improvement opportunity, whatever the reason, it is important to let them know about the change.

The Study stage is where you’ll perform analysis of the data you collected during the Do stage.

Assess the measurements and report the results to decision makers

Although act has the same meaning with do, in this stage 'Act' is meant to apply actions to the outcome for necessary improvement, in other words 'Act' means 'Improve'.