Reliability - The ability of a system or component to perform its required functions under stated conditions for a specified period of time.
The trustworthiness to do what the system is expected or designed to do. Reliability metrics include the following averages:
POFOD (Probability Of Failure On Demand) The likelihood that the system will fail when a user requests service. A biometric authentication device that fails to correctly identify or reject users an average of once out of a hundred times has a POFOD of 1%.
ROCOF (Rate Of Failure Occurrence) The number of unexpected events over a particular time of operation. A firewall that crashes an average of five times every 1,000 hours has a ROCOF of 5 per 1,000 hours.
AVAIL (availability or uptime) The percentage of time that a system is available for use, taking into account planned and unplanned downtime. If a system is down an average of four hours out of 100 hours of operation, its AVAIL is 96%.
Reliability concerns quality or consistency. Most often it concerns the consistency or dependability of a measurement or service. Reliability can be found by looking for internal consistency which can be found using tests such as the split-half method, or by looking for stability, which might be measured using the test-retest method.
- In statistics, the reliability of a set of data;
- In experimentation, the reliability of an experiment.
- For telecommunications, see unreliable.
- As the theme of The Reliable Source?, reliability means the opposite of itself. In this realm, "reliability" is a positive characteristic that is attributed without regard to the actual, literal reliability of a subject. Often, subjects reliably spontaneous, inconsistent and even decidedly unreliable are celebrated for this alter-reliability. The Reliable Source? itself is reliably inconsistent in almost every aspect (save its consistent unreliability). Published irregularly by a revolving band of writers, disinterested in anything that resembles journalistic integrity, often disguised behind strange pseudonyms and all-around false aliases.
- Reliability of a decision?
Also see these discussion threads:
"Reliability - Definition(s) (quality assurance related)"
"Reliability Definition - A Discussion thread" for further thoughts and general discussion(s) about Reliability.