Week 9 Flashcards
What is Risk?
Risk is a combination of events and the consequences of these events and the associated uncertainties.
What is the AND Gate?
The output occurs only if all of the inputs occur together.
For example: if two coins are flipped, the chance of both being heads is 0.5 x 0.5 = 0.25
What is the OR Gate?
The output occurs only if at least one of the inputs occurs.
What are Cut Sets?
CS: set of events that together cause the top undesired event to occur.
Cut Set order: number of items in a CS.
eg: Cut Sets: A - order 1 - single point failure.
B,D - order 2
- A low-order CS indicates high safety vulnerability.
- A high-order CS indicates low safety vulnerability.
What is a Reactive FTA?
A reactive fault tree analysis:
- Performed after an accident has occurred.
- Used as an accident investigation method.
What is a Proactive FTA?
A proactive fault tree analysis:
- Performed during system development to influence design by predicting and preventing future problems.
- Used as risk analysis method
What is a FTA?
Fault Tree Analysis: Is a system analysis technique used to determine the root causes and probability of occurrence of a specified undesired event.
Deductive, it transverses from the general problem to the specific causes.
What is ETA?
Event Tree Analysis: Is an inductive procedure that shows all possible outcomes resulting from an accidental (initiating) event, taking into account whether installed safety barriers are functioning or not, and additional events and factors.
ETA can be used to identify all potential accident scenarios and sequences in a complex system.
What are Markov Chains?
Markov chains are used to compute the probabilities of events occurring by viewing them as states transitioning into other states, or transitioning into the same state as before.
In a Markov Chain, the future depends only upon the present: NOT upon the past.
Where are Markov Chains used?
- Predicting traffic flows
- Cruise control systems in motor vehicles
- Currency exchange rates
- Animal population dynamics
- Queues or lines of customers arriving at an airport
- Genetic issues
- Communications networks load
What is a regular markov chain?
If its transition matrix is regular. A transition matrix P is regular if some power of P has only positive entries.
What are absorbing markov states?
A state (S) is called an absorbing state if once the state is entered it is impossible to leave.
Definitions:
1) There is at minimum one absorbing state
2) It is possible to go from each non-absorbing state to at least one absorbing state in a finite number of steps.
What is a Pre-posterior Analysis?
A decision is ‘sensitive’ if:
- after a test the decision is different for different test results
- after more tests, the decision changes
Sensitivity of the decision will tend to reduce with the increase in number of tests.
One can do a test, incur the cost of that test, and then make a decision to take a particular action or do another test.
Two types of uncertainty
Aleatory uncertainty - natural randomness
Epistemic uncertainty - inaccuracy in our understanding and our models for predicting reality.
Uncertainty that arises from the mind.
What is Utility?
The state of being satisfied, useful, valuable, profitable, having worth or beneficial.
Marginal utility (MU) is defined as the additional utility gained from the consumption of one additional unit of good service.
Total utility (TU) is defined as the total amount of satisfaction that a person can receive from the consumption of all units of a specific product or service.
When hiring a person companies compare marginal benefits to marginal costs.
Another way of thing about it is how much additional income $$ vs additional costs $$
