Lecture 3 Flashcards
What is uncertainty?
Uncertainty can be defined as the lack of exact knowledge that would enable us to reach a perfectly reliable solution
Sources of Uncertainty:
Weak implications
Vague associations between IF (condition) and THEN (action) parts of the rules.
Example 1: If Frank is bold, then he is tall? How certain?
Need to include certainty factors to indicate a degree of correlation!
Sources of Uncertainty:
Imprecise language
It can be difficult to express knowledge in the precise IF-THEN from of rules.
In real life, we describe facts with various terms such as often, sometimes, frequently, ……
Sources of Uncertainty:
Unknown data
When data are incomplete or missing, the only solution is to accept the value “unknown” and proceed to approximate reasoning with this value.
Sources of Uncertainty:
Combining the views of different experts
Experts seldom reach exactly the same conclusions.
They often have contradictory opinions and produce conflicting rules.
To resolve the conflict one has to attach a weight to each expert and then calculate the composite conclusion.
No systematic method exists to obtain weights.
Probability?
The concept of probability is associated with words like “probably”, “likely”, “maybe”, “perhaps”, “possibly”.
The probability of an event is the proportion of cases in which the event occurs. It’s a scientific measure of chance.
It can be expressed mathematically as a numerical index with a range between zero to unity (absolute certainty)
How is fuzzy logic determined
Fuzzy logic is determined as a set of mathematical principles for knowledge representation based on the degree of membership rather than on crisp membership of classical binary logic.
