Risk ranking and subjective risk assessment

Ullrika Sahlin

2024-09-06

Linquistic uncertainty

Impact on biodiversity is high

There is a 30% probability of rain tomorrow

• Prominent in qualitative risk assessment due to the use of qualitative expressions

• Can be avoided by using well defined questions, quantities and outcomes and meaningful scales

Subjective Risk Assessment

A tool from Mark and his colleagues to reduce linguistic uncertainty

SRA tool manual

Likelihood and impact scales

Subjective Risk Assessment

Rain - Rain tomorrow

Rocket - Next moon rocket crash on earth

Trump - Trump becomes the next president of USA

Use these likelihood and impact scales

Make judgements with single scores e.g. 3 or ranges, e.g. 2-4

Delphi process to aggregate judgements from a group of experts

• Make individual judgements
• Compare where there are large differences in judgements. - Discuss and resolve the reason for differences. Here is where linguistic uncertainties can be reduced.
• Redo individual judgements
• Aggregate the judgements

Interpretation of probability

Tutorial on uncertainty where Ullrika explains probability distribution

the frequency with which sampled values arise within a specified range or for a specified category

a quantification of a judgement on the likelihood of a particular range or category

Note

The mathematical theory for probability is the same for both interpretations!

Probability distributions

Visualising probability distributions

Uncertainty and variability