Editing Safety engineering (section)

====Failure modes and effects analysis====
{{Main|Failure mode and effects analysis}}
Failure Mode and Effects Analysis (FMEA) is a bottom-up, [[inductive reasoning|inductive]] analytical method which may be performed at either the functional or piece-part level. For functional FMEA, failure modes are identified for each function in a system or equipment item, usually with the help of a functional [[block diagram]]. For piece-part FMEA, failure modes are identified for each piece-part component (such as a valve, connector, resistor, or diode). The effects of the failure mode are described, and assigned a probability based on the [[failure rate]] and failure mode ratio of the function or component. This quantization is difficult for software ---a bug exists or not, and the failure models used for hardware components do not apply.  Temperature and age and manufacturing variability affect a resistor; they do not affect software.

Failure modes with identical effects can be combined and summarized in a Failure Mode Effects Summary. When combined with criticality analysis, FMEA is known as [[Failure Mode, Effects, and Criticality Analysis]] or FMECA.