Probability

Question 1

Probability

Answer 1

• a number that describes the chance of an event happening

Question 2

Pr(E) or P(E)

Answer 2

• the probability of event “E”

- always between 0 and 1

Question 3

2 ways to think about Probability

Answer 3

1. # of times E occurs/ # of times chance operation is repeated
2. # of ways the event can occur/ # of possible outcomes

Question 4

Multiplication Rule

Answer 4

• if 2 events E1 and E2 are independent, then:

Pr(E1 and E2)= Pr(E1) x Pr(E2)

Question 5

Conditional Probability

Answer 5

• Interested in “ what is the probability that Event A happens GIVEN that event B has happened.
• ”|” means “given”
• Pr{E2|E1}= (Pr{E1 and E2})/(Pr{E1})