In many cases, performing actual experiments can be much too costly and cumbersome. Instead, there might be a computer simulation of the system available which could be used as a means to generate the response values at each design point -- as an proxy for the real system output. Generally, there are two types of simulation models: Deterministic and Stochastic. Deterministic simulation models are usually complex mathematical models which provide deterministic outputs and not a random variable. The output from a stochastic simulation model is a random variable. Normally, and for optimization purposes, a program of the simulation model is built (which is called Metamodel) and based on the assumption that the simulation model is a true representation of reality, the achieved optimum condition should be in compliance with the real system. Research into optimal designs for complex models and optimal interpolation of the model output have become hot areas of research in recent years. However, in this course we will not cover any details about “experiments with computer models." More information can be found in the text and of course the relative references.