The Plan-Do-Check-Act is an iterative four-step management method used in business for the control and continual improvement of processes and products.
The concept of PDCA is based on the scientific method, as developed from the work of Francis Bacon (Novum Organum, 1620) and can be written as hypothesis–experiment–evaluation or as plan–do–check. Walter A. Shewhart described manufacture under (statistical) control as a three-step process of specification, production and inspection.
A fundamental principle here is iteration - once a hypothesis is confirmed (or negated), executing the cycle again will extend the knowledge further. Repeating the PDCA cycle can bring its users closer to the goal, usually a perfect operation and output.