R I S K
Combining the ‘probability’ and ‘impact’ of a risk in order to define its ‘size’ is standard practice. But in most cases it’s irrational, and it certainly would not have explained to Bruce Willis and his crew ,for destroying the meteor in the film Armageddon ,why their mission made sense. To get rational measures of risk you need a causal model (‘risk map’) that links triggers, controls, events, mitigants and consequences. Once you do this measuring risk starts to make sense – and it’s much easier.
Trigger := Meteor on Collusion course;
Risk Event:= Meteor strikes Earth;
Consequences:= Loss of Life;
Now on our hand........
Control:= Blow Up meteor (by atom bomb);
Mitigant:= Build Underground Cities;
The causal, risk map approach satisfies minimalist requirements described by Chapman and Ward in
[Chapman C and Ward S, ‘Estimation and evaluation of uncertainty: a minimalist first pass approach’, International Journal of Project Management, 18, 369-383, 2000]
Where they recommend that any approach to risk quantification:
“should be so easy to use that the usual resistance to appropriate quantification based on lack of data and lack of comfort with subjective probabilities is overcome”.
Moreover, the approach ensures that:
Every aspect of risk measurement is meaningful in the context – the risk map tells a story that makes sense.
THIS IS IN STARK CONTRAST WITH THE
“risk = probability x impact” approach where not one of the concepts has a clear unambiguous interpretation.