Risiko COPY COPY Flashcards
What is risk?
Risk = combination of consequences and associated uncertainties
What are the risk concept and its denotation
(C, U) = Consequences with respect to something of value
OR
(A, C, U) = Consequences with respect to something of value, given the event A
What is the general risk description and what is Risk described by?
Risk description = (A’, C’, P, SoK, K)
Risk is described by = (C’, Q, K) and (A’ C’, Q, K)
What do the different variables mean?
A’ = Specified events
C’ = Specified consequences
Q = Uncertainty measure describing uncertainties related to A’ and C’. Commonly represented by (P, Sok).
P = Probability
SoK = Strength of knowledge
K = Knowledge that Q and (A’, C’) are based on.
Describe some common risk metrics
E[C’] = Expected value
Ef[C] = Average value of return if one runs a project an infinite (or large) amount of times.
VaR = Value at Risk
PLL = Potential loss of lives in a period of one year
FAR = Fatal accident rate. Expected number of fatalities per 100 million exposed hours.
What are the formulas for PLL and FAR?
PLL = n * IR
n = number of equally exposed individuals
IR = probability that a specific person is killed in a year
FAR = Fatalities pr. exposed hour * 100 million
OR
FAR = (PLL / Number of exposed hours) * 100 million
Define a frequentist probability
Pf(A) = Number of times A would occur when repeating situations over and over nearing infinite.
Define subjective/knowledge-based probability
A probability expresses a person’s uncertainty or degree of belief that an event will occur. The person compares the uncertainty or belief related to event A.
What is a crucial assumption related to the underlying value in frequentist probabilities?
The value needs to be estimated as the underlying true value is generally not known.
Define Resilience
The ability of a system to sustain or restore its basic functionality following an event (risk source).
Define Vulnerability
Vulnerability is essentially risk conditioned on the occurrence of an event A.
What is the description of vulnerability?
Vulnerability = (C, U|A)
What is the connection between Resilience and Vulnerability?
Resilience reflect an aspect of vulnerability by focusing on the systems ability to recover after an event A.
Define Reliability
A system’s ability to work as intended
In what way is safety the antonym of risk?
High safety = Low Risk
Low Safety = High Risk
What does the term “Safe and secure” mean in practice?
The term “Safe and Secure” means that the risk is acceptable/tolerable
What is a Risk matrix? And, what are some of its common limitations?
Risk matrix:
Matrix that illustrates risk by different events, using the probability of the event ( P(A’) ), and conditional expected value ( E[C’|A] ).
Limitations:
*Does not reflect the spectre of consequences and lacks considerations of the SoK
*Often, are events poorly plotted and not well defined
*Colour schemes should generally be avoided as they are potentially misleading
*Consequences of an event are not properly represented by one point in the matrix.
*Two events could have same location in matrix, but have vastly different supporting knowledge and consequences.
What is a Risk assessment?
Methods and approaches for improving our understanding of risks and supporting decision-makers.
What is the benefit of a risk assessment?
Risk assessments can help identify what may go wrong, why and how, what are the consequences and how bad are they.
What are the different stages in a Risk assessment?
- Planning - Establishing context
- Risk analysis & Risk Evaluation
- Utilization of risk assessment
Explain what the term “management review and judgement” (MRJ) is
MRJ is the process between a risk assessment and consequent decision-making.
The MRJ process considers the limitations of the risk assessment. One summarises, interprets and deliberate the risk assessment results such that the results are prepared for decision makers.
What is a model-based risk assessment? What is their purpose?
Model-based risk assessments are used to understand how a given system functions.
They aim to increase risk understanding by allowing us to change input quantities and measure the effect of risk-reducing measures.
List the different examples of model based risk assessments
- Event trees - Assess possible outcomes, associated probabilities
- Fault trees - Assess the probability of failure in a safety barrier.
- Block diagram
- SWIFT - Identify the events leading up to a later event
- FMEA - Identify and rank failure modes for a system
What are the basic symbols in a fault tree, and what is their meaning?
Circle - Basic event - Event at the lowest level in the model
Bowed square - And gate - The output event (above) occurs if all outputs (below) occur.
Bowed Triangle - Or gate - The output event (above) occurs if at least one of the input events (below) occurs.
Triangle - Transfer symbol - Used when the same branch occurs at several places in the tree, and when the tree must be drawn on several pages.
Rectangle - Description of event/state - Placed above gates and basic events.
