The Probability of Kill (or Pk) is usually based on a Uniform random number generator. This algorithm creates a number between 0 and 1 that is approximately uniformly distributed in that space. If the Pk of a weapon/target engagement is 30% (or 0.30), then every random number generated that is less that 0.3 is considered a kill. Every number greater than 0.3 is considered a "not kill". When used many times in a simulation, the average result will be that 30% of the weapon/target engagements will be a kill and 70% will not be a kill.
This measure may also be used to express the accuracy of a weapon system. For example, if a weapon is expected to hit and kill a target nine times out of ten with a representative set of ten engagements, one could say that this weapon has a “Pk” of 0.9. If the percentage of hits is nine out of ten, but the probability of a kill with a hit is .5, then the Pk becomes .45 or 45%. This reflects the fact that even modern warheads may not always destroy a target such as an aircraft, missile or main battle tank.