Page "Risk management" Paragraph 57

The probability of occurrence is likewise commonly assessed on a scale from 1 to 5, where 1 represents a very low probability of the risk event actually occurring while 5 represents a very high probability of occurrence.

This axis may be expressed in either mathematical terms ( event occurs once a year, once in ten years, once in 100 years etc.

) or may be expressed in " plain english " – event has occurred here very often ; event has been known to occur here ; event has been known to occur in the industry etc .).

Again, the 1 to 5 scale can be arbitrary or non-linear depending on decisions by subject-matter experts.