Developing Probabilities

Hardware failure data and human error probabilities (HEPs) are available, but sometimes risk analysts have to dig for them. Hardware failure rate data is available from a variety of sources including handbooks, databases, research reports, and findings from accident investigations. HEPs are available from standardized human reliability analysis processes like technique for human error‐rate prediction, and they can be developed using tools like the Delphi process. The main point of this chapter is to use the best data available for risk assessments. In the truest sense, hardware failure data is much easier to obtain than is HEPs. In many cases, failure rate data is available at the system as well as the subsystem and component levels. Hardware failure rate data can be obtained from the manufacture, from historical data, government and military handbooks, accident data or generated from testing by the user.