Editing Failure rate (section)

===Other models===

[[File:Loglogistichaz.svg|thumb|right|300px|Hazard function <math>h(t)</math> plotted for a selection of [[log-logistic distribution]]s, any of which could be used as a hazard rate, depending on the system under study.]]

For many systems, a constant hazard function may not be a realistic approximation; the chance of failure of an individual component may depend on its age. Therefore, other distributions are often used.

For example, the [[deterministic distribution]] increases hazard rate over time (for systems where wear-out is the most important factor), while the [[Pareto distribution]] decreases it (for systems where early-life failures are more common). The commonly-used [[Weibull distribution]] combines both of these effects, as do the [[log-normal distribution|log-normal]] and [[Hypertabastic survival models|hypertabastic]] distributions.

After modelling a given distribution and parameters for <math>h(t)</math>, the failure probability density <math>f(t)</math> and cumulative failure distribution <math>F(t)</math> can be predicted using the given equations.