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NAME:
11
e) (4 pt)
You now want to compute the distribution
P
(
A
) using variable elimination. List the factors that
remain before and after eliminating the variable
N
.
Before:
The initial factors are just the conditional probability tables of the Bayes’ net.
P
(
A
),
P
(
P

A
),
P
(
C

A
),
P
(
T

C
),
P
(
N

P,C
),
P
(
E

T,N
)
After:
First, all factors that include the variable
N
are joined together, yielding
P
(
E,N

P,C,T
)
Next, the variable
N
is summed out of this new factor, yielding
P
(
E

P,C,T
)
The remaining factors include this new factor and the unused original factors.
P
(
A
),
P
(
P

A
),
P
(
C

A
),
P
(
T

C
),
P
(
E

P,C,T
)
Referring to the ﬁnal factor as
m
(
E,P,C,T
)
(like in the textbook) was also accepted.
f) (2 pt)
Pacman’s new diet allows only fruit (
P
and
A
) to be eaten, but Pacman only follows the diet
occasionally. Add the new variable
D
(for whether he follows the diet) to the network below by adding arcs.
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This note was uploaded on 08/30/2009 for the course CS 188 taught by Professor Staff during the Spring '08 term at University of California, Berkeley.
 Spring '08
 Staff
 Artificial Intelligence

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