Simulation and modeling - Old Questions

4.  Define model. Describe different types of simulation models in brief.

Model is a computerized program that defines the mechanics of the considered system. It must have state which may change on each time step. Model represents the system for the purpose of studying the system.

A simulation model can be classified as being static or dynamic, deterministic or stochastic, and discrete or continuous.

• A static simulation model, sometimes called a Monte Carlo simulation, represent a system at a particular point in time. For example, the profit of a company, which is affected by 3 variables drawn from different statistics distributions.
• A dynamic simulation model represents a system as it changes over time. For example, the simulation of a bank from 9 am to 4 pm.
• Deterministic model contains no random variables. They have a known set of inputs which will result in a unique set of outputs. E.g. Arrival of patients to the Dentist at the scheduled appointment time.
• Stochastic model has one or more random variable as inputs. Random inputs leads to random outputs. E.g. Simulation of a bank involves random inter-arrival and service times.
• Discrete model is one in which the state variables changes only at a discrete set of time. For example: banking system in which no of customers (state variable) changes only when a customer arrives or service provided to customer i.e. customer depart form system.
• Continuous model is one in which the state variables change continuously over time. For example, during winter seasons level of which water decreases gradually and during rainy season level of water increase gradually. The change in water level is continuous.