What
ʼ
s the probability that the
next candy is lime?
1
CS440/ECE448: Intro AI
What is
P(d
i+1
 d
1
,…, d
i
) = P(X 
D
)?
We don
ʼ
t know which bag of candy we got, so we
have to assume it could be any one of them:
P(X 
D
) =
!
i
P(X 
D
, h
i
)P(h
i

D)
=
!
i
P(X  h
i
)P(h
i

D)
Lecture 19
Learning graphical
models
Prof. Julia Hockenmaier
[email protected]
http://cs.illinois.edu/fa11/cs440
CS440/ECE448: Intro to ArtiFcial Intelligence
The
Burglary
example
3
CS440/ECE448: Intro AI
Burglary
Earthquake
Alarm
JohnCalls
MaryCalls
!"#
!"%
&''(
'&)))
*"#
*"%
&''+
'&)),
!
*
"#
"%
#
#
&).
&'.
#
%
&)/
&'0
%
#
&+)
&1(
%
%
&)))
&''(

2"#
2"%
#
&1
&3
%
&'(
&))

4"#
4"%
#
&)
&(
%
&'.
&).
What is the probability of a burglary if John and Mary call?
Learning Bayes Nets
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View Full DocumentHow do we know the parameters
of a Bayes Net?
We want to estimate the parameters based
on
data
D.
Data = instantiations of some or all random
variables in the Bayes Net.
The data are our evidence.
Surprise Candy
There are two Favors of Surprise Candy: cherry
and lime. Both have the same wrapper.
There are ±ve different types of bags (which all
look the same) that Surprise Candy is sold in:
–
h1: 100% cherry
–
h2: 75% cherry + 25% lime
–
h3: 50% cherry + 50% lime
–
h4: 25% cherry + 75% lime
–
h5: 100% lime
6
CS440/ECE448: Intro AI
Surprise Candy
You just bought a bag of Surprise Candy.
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 Spring '08
 Levinson,S
 Conditional Probability, Likelihood function, Burglary, Intro AI

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