In the field of engineering, whether it be designing a bridge, a computer system, or even an entire world, precise mathematical methods are available to assist engineers in their efforts to produce a creation that is both practical and robust. Exact calculations are made to determine the minimum amount of material and resources (including labor) needed to achieve the desired results, while keeping the costs as low as possible.

For instance, many factors are taken into account when designing a bridge for automobiles. There is a maximum load it must be able to support, so if there is a traffic jam of nothing but heavy trucks, the bridge will support them. If a storm or earthquake as strong as the worse ever recorded for the area hits, the bridge will survive it. Many, many such calculations are made including interactions between events, like what happens when a storm hits while the bridge is jammed with trucks.

Engineered products are seldom built from these minimum specifications though. If they were, the slightest miscalculation, imperfection in material, construction flaw or deterioration due to aging and corrosion could cause catastrophic failure. For that reason, the creations are designed to exceed the minimum requirements. In other words, they are “overbuilt” to a degree. The difference between the theoretical minimum and final specifications is called “The Safety Factor”.