Using simultaneous higher-level and partial lower-level data in reliability assessments

When a system is tested, besides system data, some lower-level data may become available such as a particular subsystem or component was successful or failed. Treating such simultaneous multi-level data as independent is a mistake because they are dependent. In this paper, we show how to handle simultaneous multi-level data correctly in a reliability assessment. We do this by determining what information the simultaneous data provides in terms of the component reliabilities using generalized cut sets. We illustrate this methodology with an example of a low-pressure coolant injection system using a Bayesian approach to make reliability assessments.