Reliability theory developed apart from the mainstream of probability and statistics, and was used originally as a tool to help nineteenth century
maritime insurance and life insurance companies compute profitable rates to charge their customers.
Even today, the terms "failure rate" and "hazard rate" are often
The failure of mechanical devices such as ships, trains, cars, and so on, is similar in many ways to the life or death of biological organisms.
Statistical models appropriate for any of these topics are generically called "time-to-event" models.
Death or failure is called an "event", and the goal is to project or forecast the rate of events for a given population or probability of an event for an individual.
It should be noted that when reliability is considered from the perspective of the consumer of a technology or service, actual reliability measures may differ dramatically from perceived reliability. One bad experience has the psychological effect of magnifying the perceived un-reliability of the technology or service. For example, one plane crash, where hundreds of passengers die, will immediately instill fear in a large percentage of the flying consumer population, regardless of actual reliability data about the safety of air travel.
Computer software exists to quantify complex system reliability.