(9d) How Extreme Failure-Data Filtering Leads to Poor Process Safety

This paper describes both appropriate and inappropriate practices of filtering field failure data (FFD) prior to using the resulting failure count from the failure data to estimate failure rates. The underlying causes of inappropriate (extreme) filtering of FFD are examined and the consequences (poor process safety) are discussed. An example is presented illustrating the benefits of using all real failures discovered in the field in the estimation of failure rates based on FFD.