A broad collection of methods used to study and analyze the behavior and performance of actual or theoretical systems. Simulation studies are performed, not on the real-world system, but on a (usually computer-based) model of the system created for the purpose of studying certain system dynamics and characteristics. Simulation is both an experimental science and an art or craft in the development of the precise, “valid” model that captures the necessary elements of the system, and the use of the model to analyze system behavior under various scenarios.