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 used interchangeably. The word probability derives from the Latin probare (to prove, or to test). ... Statistics is a type of data analysis whose practice includes the planning, summarizing, and interpreting of observations of a system possibly followed by predicting or forecasting of future events based on a mathematical model of the system being observed. ... Life insurance is a type of insurance. ... Exponential failure density functions Failure rate describes how frequently something fails. ...

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.

See also

• availability
• extreme value theory
• failure rate
• fault tree
• Gompertz law
• mean time between failures
• reliability
• reliability engineering
• survival analysis
• Weibull distribution
• Bathtub curve

In telecommunications and Reliability theory, the term availability has the following meanings: 1. ... Extreme value theory is a branch of statistics dealing with the extreme deviations from the median of probability distributions. ... Exponential failure density functions Failure rate describes how frequently something fails. ... Safety engineering is used to assure that a life-critical system behaves as needed even when pieces fail. ... By using Mediterranean fruit flies, Gompertzs 1825 theory that mortality rates increase at an exponential rate as age increases is examined. ... In engineering and telecommunication, the mean time between failures (MTBF) is the average time a system will operate without a failure. ... In engineering in general, reliability is the capacity of a component or a system of such components to perform as designed. ... Reliability engineering is the discipline of ensuring that a system will be reliable when operated in a specified manner. ... Survival analysis is a branch of statistics which deals with death in biological organisms and failure in mechanical systems. ... In probability theory and statistics, the Weibull distribution (named after Waloddi Weibull) is a continuous probability distribution with the probability density function where k >0 is the shape parameter and λ > 0 is the scale parameter of the distribution. ... In reliability theory, the bathtub curve is the phenomenon that the fraction of products failing in a given timespan is usually high early in the lifecycle, low in the middle, and rising strongly towards the end. ...

External links

• Reliability theory applied to aging and death
• Reliability and Availability Basics
• System Reliability and Availability