In quality management, a four-step process for quality improvement. In the first step (plan) , a plan to affect improvement is developed. In the second step (do) , the plan is carried out, preferably on a small scale. In the third step (check) , the effects of the plan are observed. In the last step (action) , the results are studied to determine what was learned and what can be predicted. The plan-do-check-act cycle is sometimes referred to as the Shewhart cycle (Walter A. Shewhart discussed the concept in his book Statistical Method from the Viewpoint of Quality Control) and as the Deming circle (W. Edwards Deming introduced the concept in Japan; the Japanese subsequently called it the Deming circle) . Synonym: Shewhart Cycle. Also see: Deming Circle.