10 Mar 2004
CS 3243 - Uncertainty
10
Prior probability
nPrior
or unconditional probabilities of
propositions
e.g., P(Cavity = true)
= 0.1 and P(Weather = sunny) = 0.72 correspond to belief prior to arrival of any (new) evidence
nProbability distribution gives values for all possible assignments:
P(Weather) = <0.72,0.1,0.08,0.1> (normalized,
i.e., sums to 1)
nJoint probability distribution for a set of random variables gives the probability of every atomic event on those random variables
P(Weather,Cavity) = a 4 × 2 matrix of values:
Weather = sunny rainy cloudy snow
Cavity = true 0.144 0.02 0.016 0.02
Cavity = false 0.576 0.08 0.064 0.08
nEvery question about
a domain can be answered by the joint distribution
