Missile accuracy is defined by a quantity known as Circular Error Probable (CEP). Imagine a target, with a number of warheads fired at it. The warheads will produce a scatter around the target: the greater the scatter, the more inaccurate the missile. CEP is a measure of that scatter. CEP is the average distance within which 50% of all incoming warheads can be expected to land. Most missiles have CEPs under 1,000 feet. The U.S. MX/Peacekeeper missile has a CEP of 260 feet.
