Paper: Uncertainty bridging troubled waters by Inger Lise Johansen & Marvin Rausand Comments by Jørn

Transcription

1 Paper: Uncertainty bridging troubled waters by Inger Lise Johansen & Marvin Rausand Comments by Jørn : I like the discussions and presentation of different positions : I am not that happy with all the propositions

2 What is risk? Q Inger Lise = Kaplan [23] Jørn [41] 1 What can happen? Uncertainty regarding WHAT can happen 2 How likely is it? Uncertainty regarding IF it happens 3 If it does happen, what are the consequences? Uncertainty regarding the severity, GIVEN that it happen Jørn: Risk = uncertainty regarding what, if (and why!) and so what. Uncertainty is expressed by probabilities. Uncertainty is the baseline, not how likely.

3 Inger Lise: Uncertainty is a premise for expressing risk, or uncertainty is a limitation in the expression of risk Important clarification. What is then the position taken by Inger Lise regarding the interpretation of risk? Explicitly, I cannot find the answer, but: In this paper, we adopt the definition of complexity established in Johansen and Rausand [22]: Acknowledgment of limitations in the understanding of a system and (jørn: limitations in the understanding of) its risk given knowledge and assumptions about individual elements. Implicitly, therefore I deduce that there are limitations in the understanding of risk according to Inger Lise, complexity conceals aspects of risk, and it is difficult to interpret Inger Lise s understanding risk as something different form a true risk.

4 Presenting risk: From Kaplan, introduce events (e i ), probabilities (p i ) describing the uncertainty regarding occurrence of the events, and finally the severity with respect to the values at stake (S i ). This yields the quantitative unconditional expression of risk:,, An unconditional uncertainty statement is of limited value. Jørn therefore proposes to present a conditional risk statement:,, D, U, V Where D = dialog processes and risk communication among stakeholders that elaborate on the values and preferences domain and what is values are at stake (e.g., fatalities). U = the relevant information, the theories, the understanding, and the assumptions which are the basis for the risk assessor (premises for expressing uncertainty), and V = verification processes This is different from Inger Lise, who presents a definition of risk that is unconditional

5 Inger Lise: Our bold claim is that to the decision maker, it does not really matter whether this is in comparison with a true risk or a subjective expression of uncertainty; what matters is whether the analysis gives relevant information and has a sound basis. This can be considered as a third interpretation of uncertainty that is defined not in relation to risk as such, but in the analyst s confidence. Such confidence is in our view the ultimate purpose of risk assessment and by that any consideration of uncertainty. Jørn: Confidence for whom?

6 Should we care about the decision maker? 1. The parachute dilemma. Airplane fire. Two parachutes A and B, which one to use? A = Proven technology, q = Pr(Fails to open) = B = New model, we are uncertain regarding the true reliability, i.e., Pr(Q=10 2 ) = 7%, Pr(Q=10 4 ) = 93%. E(Q) , CV(Q) 3. A true risk approach: The true risk, q A = 10 3 = known, the true risk, q B = unknown, but estimated to which is slightly lower than for A, but since we generally are risk averse (don t like uncertainty), the high uncertainty CV(Q B ) 3 favors A jump with A (and maximize the probability of dying). A subjective uncertainty approach to risk; assess Pr(Dying A, D, U, V) = 10 3, Pr(Dying B, D, U, V) < 10 3, jump with B (and minimize the probability of dying) 2. Interpretation issue. If it for the researcher is not clear what is meant by a true risk, we should not please the decision maker and give him something we cannot really stay behind. Therefore, the researcher (Inger Lise) needs to be comfortable with a concept of true risk. 3. Implication for interdisciplinary research. Accepting the idea of true risk, also implies that there are systems for which true risk does not exist, e.g., intractable systems, Perrowian systems etc. Many researchers therefore claim that risk analysis is inappropriate for such systems, making interdisciplinary research impossible.

7 What is Analyst s confidence. Jørn: D, U, V Inger Lise proposes a definition of uncertainty that includes aspects of D, U, V in her definition: Uncertainty: Lack of certainty with respect to: 1) knowledge about the future state and behavior of the system and 2) the soundness and relevance of the results in a specific decision context. Comments (i) For the first part: what is the difference in interpretation between: 1. Lack of certainty with respect to the future state and behavior of the system 2. Lack of knowledge about the future state and behavior of the system 3. Lack of certainty with respect to: 1) knowledge about the future state and behavior of the system (ii) Why future state and behavior, and not only state and behavior (today s uncertainty)? (iii) Second part: 2) the soundness and relevance of the results. I cannot see that this is anything different from D, U, V in Jørn s definition of the conditional risk, i.e., the conditions for stating uncertainty.

8 Proposal for further investigation (in PhD) 1. Prepare a worked example, covering major aspects of the IRGC framework 2. Clarify and exemplify the term ambiguity with respect to all the three questions related to risk, both in a true risk understanding, and when risk is entirely understood as uncertainty. 3. Argue why the introduction of ambiguity is a more basic point of departure than for example D, U, V

9 What is the understanding of overlap?