You start off by designing a table with one leg, because that saves on material. But you also knock off designs for tables with three legs and four legs. You run the analysis and find the table with one leg does as well as the table with four legs. So you start refining that design. In this case, the engineer has specified that the table hold a computer's weight and that it use as little material as possible.
Quick analysis determines that a one-legged table is a practical table.
But then the designer goes further, by interrogating the system with a number of what-if scenario questions. The analysis program runs those numbers and is able to present the engineer with numerical comparisons. The designer may find that a three-inch table may not be necessary to hold the computer's weight. Better to model the product, test for potential flaws, and remodel on the computer than to build prototype after prototype, he added. Simulation modeling can also shave design time.