Some Limitations of Frequency as a Component of Risk: An Expository Note

Students of risk analysis are often taught that “risk is frequency times consequence” or, more generally, that risk is determined by the frequency and severity of adverse consequences. But is it? This expository note reviews the concepts of frequency as average annual occurrence rate and as the reciprocal of mean time to failure (MTTF) or mean time between failures (MTBF) in a renewal process. It points out that if two risks (represented as two...