ABSTRACT
The term “failure” refers to the degradation of the performance of a device outside a specied value. It may be dened as:
This denition contains several interesting concepts. It assumes the normal function of the device has been dened. If the function of the device has not been speci-ed, then a failure, or deviation from that intended function cannot be established. The denition also assumes the environmental conditions under which the system or component will operate have been specied. This includes environmental parameters such as temperature, lighting, ambient noise, stress level under which the user is operating, interference from other equipment in the area, and interference to other equipment in the area. Some or all may play an important part in determining when the system or component is experiencing a failure and when it is not.
