Design of experiments is described in the PMBOK Guide [23] as a “statistical method that helps identify which factors may influence specific variables of a product or process”. Modeling (including experimental models, prototypes, pilot plants, computer simulation models, three-dimensional scale models, full-scale models and mathematical models) is a much wider concept and is much more widely used in the development of engineering systems but is unfortunately not yet recognized in PMBOK Guide [23] and other standards.