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Foundations of risk and reliability assessment and management Terje Aven University of Stavanger, Norway
Foundations of risk and reliability assessment
and management
Terje Aven
University of Stavanger, Norway
Kahneman
asserts that we
have a basic
lack of ability to
treat small risks:
we either ignore
them completely
or give them too
much weight.
The main thesis
put forward is
that we grossly
over-estimate
small risks.
Kahneman’
s book
«Thinking
fast and
slow»
Israel 2001-2004: 23 bombings, 236 fatalities. The number of daily bus riders in Israel was approximately 1.3 million at that time.
For any traveler, the risks were tiny,
but that was not how the public felt about it. People avoided buses as much as they could…
I knew that the risk
was truly negligible, and that any effect at
all on my actions would assign an
inordinately high “decision weight” to a
minuscule probability.
In fact, I was more likely to be injured in a driving accident than by
stopping near a bus. But my avoidance of buses was not motivated
by a rational concern for
survival.
Risk
Is not uncertainty a main component ofrisk ?
Foundations of risk and reliability assessment
and management
Examples of issues
• How to understand and describe risk and reliability
• How to understand and treat model uncertainty
• How to treat uncertainties in risk and reliability assessments
• How to conceptualise and deal with black swans
• How to use the precautionary principle in risk management
• How to make use of signals and warnings in risk assessment and management
• Risk analysis and science
Engineering Transpor-tation
…Finance Medicine
General insights linked to risk and reliability
Generic concepts, theories, frameworks, approaches, principles and methodsfor
understanding, assessing, managing and communicating risk, reliability and uncertainties
Risk and reliability assessment and management in
different applications
Existing frameworks, principles and concepts
Theories, frameworks,
principles, methods,concepts
Today Future
Theories, frameworks,
principles, methods,
concepts
New types of systems
and risks
Revitalise the focus and enthusiasm for
fundamental issues in the risk and
reliability fields
Specialty Group of SRA (Society of Risk Analysis)
on
Foundational issues in Risk Analysis http://www.sra.org/frasg
http://www.sra.org/news/new-sra-specialty-group-created-foundational-issues-risk-analysis
Special issue of Risk Analysis
Special issue of Safety Science on foundations of safety science
Risk Analysis
Aven, T. and Zio, E. (2014) Foundational issues in risk assessment and management
10 issues that need further focus
Issue 1: Terminology
Society of Risk Analysis
Glossary
Issue 2
The appropriate representation, characterization, and interpretation of uncertainty in a risk assessment context
Samson, Reneke and Wiecek (2009)A review of different perspectives on uncertainty and risk and an alternative modeling paradigm, Reliability Engineering & System Safety 94, 558–567
Uncertaintyabout
Uncertaintyabout how tall John is
Uncertaintyabout C
C: John’s height
Uncertaintyabout C
C = outcome
Uncertaintyabout C
C = future consequencesActivity
Uncertaintyabout p
p = Pf(outcome is 6)
Uncertaintyabout P?
P(outcome is 6 |K ) = 0.1
No, but imprecision
K: backgroundknowledge
Model g(X)
C = unknown quantityActivity
Model uncertainty?
Error g(X)-C
C = unknown quantityActivity
Model uncertainty: uncertainty about this error
«Uncertainty about a phenomenon»
The link between cancer and smoking
Error g(X)-C
C = unknown quantity(number of deaths)
g(X) = model of the number ofdeaths as a function of smoking rates etc.
Model uncertainty: uncertainty about this error
Expressing the uncertainty
Probability
Frequentist
probability
Pf
Jugdmental/
knowledge-based,
subjective
probabilities P
Probability
Variation Assessor’s
expression of
uncertainty – a
degree of belief
Knowledge-based probability
• P(A|K) = 0.1
• The assessor compares his/her uncertainty (degree og
belief) about the occurrence of the event A with
drawing a specific ball from an urn that contains 10
balls (Kaplan and Garrick 1981, Lindley, 2000).
K: background knowledge
Youtube: Aven streaming about probability: http://www.youtube.com/watch?v=wp6iIdxHf_Q&list=PLNFAW9iarHu_kP9n34CSPRoUM8h1hBojp&index=3
Expressing the uncertainty
ProbabilityKnowledge supporting P
Expressing the uncertainty
Imprecise probabilitiesKnowledge supporting these
Issue 10 The science of risk assessment
• Hansson and Aven (2014) Is risk analysisscientific? Risk analysis
Science
• The practice that provides as with the most reliable statements at the time being on thesubject matter covered by the knowledgedisciplines
Risk and black swans
Engineering Transpor-tation
…Finance Medicine
General insights linked to risk and reliability
Generic concepts, theories, frameworks, approaches, principles and methodsfor
understanding, assessing, managing and communicating risk, reliability and uncertainties
Risk and reliability assessment and management in
different applications
Black Swan
A surprising, extreme event relative
to present knowledge/beliefs
Aven (2013) On the
meaning of a black swan in
a risk context. Safety
Science, 57, 44-51
Risk management implication
Risk analysisRobustness, resilience,
cautious policies …
