Benefits of a Bayesian approach to anomaly and failure investigations

It is often the case in failure and anomaly investigations that data is either limited or so wide ranging that it is difficult to bring focus to a key root cause. For this reason, a disciplined approach incorporating root cause trees (Ishikawa Diagrams) is usually taken to develop and track root cause hypotheses and analyses. During the investigation, statistical tools can be used to evaluate various hypotheses of failure. However, in many cases, there is limited failure data and it is often necessary to set up accelerated life tests involving many samples in order to induce failures under controlled conditions so that a statistically significant population of failures can be obtained. Root cause is sometimes achieved only after extensive and expensive efforts to reduce the number of root cause hypotheses. Other times, root cause investigations are truncated to “most probable cause” based on the evidence available and expert opinion.