ABSTRACT
This chapter emphasises the need to do any risk estimation thoughtfully and with real understanding of the nature of the Occurrence process. The most complex method is quantified risk analysis (QRA). The use of QRA is largely limited in practice to the analysis of the technology of complex aerospace and petrochemical ventures, although this is not an inherent limitation of the method. In quantified risk estimation, estimating the risk means deciding where to draw a line on the Risk Diagram that is a reasonable representation of the Risk in question, by estimating the Frequency associated with the Consequence. Consequence Value is complicated by the presence of unquantifiable components where human suffering and environmental damage exists. Qualitative word scales that allow a choice between ranges of possibilities, called ordinal scales, can easily be developed for each of the three parameters that define Risk. The simplest way to compare the significance of different Risks is to estimate the LWC.
