Probabilistic Reasoning; Network-based reasoning. COMPSCI 276 Fall 2007. Class Description. Instructor: Rina Dechter Days: Monday & Wednesday Time: 2:00 - 3:20 pm Class page: http://www.ics.uci.edu/~dechter/ics-275b/Fall-2007/. Why uncertainty. Summary of exceptions
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Probabilistic Reasoning;Network-based reasoning
COMPSCI 276
Fall 2007
AC
BC
---------
A and B - C
True
propositions
Uncertain
propositions
Q: Does T fly?
P(Q)?
Logic?....but how we handle exceptions
Probability: astronomical
AB: m
P(A|B) = m
A
x
If A then C (x)
If B then C (y)
If C then D (z)
z
C
D
y
B
1.Parallel Combination:
CF(C) = x+y-xy, if x,y>0
CF(C) = (x+y)/(1-min(x,y)), x,y have different sign
CF( C) = x+y+xy, if x,y<0
2. Series combination…
3.Conjunction, negation
Computational desire : locality, detachment, modularity
Burglery
Phone
call
Alarm
Earthquake
Radio
AB
A more credible
------------------
B more credible
IF Alarm Burglery
A more credible (after radion)
But B is less credible
Rule from effect to causes
Extensional
Intensional
A and BC
(m+n-mn)
P(S)
P(C|S)
P(B|S)
CPD:
P(X|C,S)
P(D|C,B)
Conditional Independencies
Efficient Representation
Smoking
lung Cancer
Bronchitis
X-ray
Dyspnoea
P(S, C, B, X, D)
= P(S) P(C|S) P(B|S) P(X|C,S) P(D|C,B)