Event tree analysis is based on discrete binary logic, in which an event is in either ON or OFF state which indicate that failure did not happen, failure happened or a component of it has not failed. It is valuable in analyzing the consequences arising from a failure or undesired event. An event tree begins with an initiating event of interest. The consequences of the event are followed through a series of possible paths. Each path is assigned a probability of occurrence and the probability of the various possible outcomes can be calculated from them.