Bayesian Probability The geometry of changing beliefs

2. P(H|E)= [P(E|H) P(H)]/P(E)
You

3. Gopal
Gopal is a very shy and withdrawn, invariably
helpful but with very little interest in people
or in the world of reality. A meek and tidy soul,
he has a need for order and structure, and a
passion for detail.
Seem bookish….. He might
be a scientist.
Scientist(90%) Farmer(10%)
You
Scientist Farmer

4. Scientist Farmer
Stereotype Unexpected

5. 200
4
20
1:20
1
0
P(Scientist given farmer )
= 4/(4+20)
= 16.7%

6. P(H|E)= [P(E|H) P(H)]/P(E)
Bayes’ rule
P(H) = Probability of a hypothesis is true (before any
evidence)
P(E|H)= Probability of seeing the evidence if the
hypothesis is true.
P(E)= Probability of seeing the evidence.
P(H|E)= Probability of hypothesis is true given some
evidence.

7. Biotechnologist
Biotechnologist

8. What is the probability of the event “both children are girls” (B) conditional on the event “the older child is a
girl” (G)?

9. “Critical thinking is an active and
ongoing process. It requires that we all
think like Bayesians, updating our
knowledge as new information comes
in.”

10. THANK
YOU