A Bayesian model represents uncertain beliefs with probability distributions and updates them when new observations arrive. The same evidence can produce different conclusions because people begin with different prior probabilities. section 3.1
The carnival psychic
Imagine a person correctly guessing a number from 0 to 9 one hundred times. For a true psychic, the likelihood of a correct guess is 1; without psychic ability, it is 1 out of 10. Each observer combines these likelihoods with a personal prior belief and updates to a posterior probability. A skeptical observer’s belief rises slowly, while someone who assigns a prior of 0 remains at 0. section 3.1
Figure 3.3 How each person’s prior belief is updated by the same data. Compared to Bob’s, your prior is much lower and increases more slowly. Alice’s prior is 0 and stays at 0 throughout.
Compare how identical observations produce different posterior beliefs when the initial priors differ. section 3.1

