3.1 - 3.3: Probability & Probability Rules

Question 1

Probability

Answer 1

• the proportion of times that an event would occur in a long run of observations; quantifies uncertainty
• 0 ≤ P(A) ≤ 1
• if P(A) = 1, then A is guarunteed to occur
• if P(A) = 0, then A is guarunteed to not occur

Question 2

Define sample space. What is set notation? What is the sum of the probabilities of all outcomes in a sample space?

Answer 2

• the set of all possible outcomes for a random phenomenon
• {1, 2, 3, 4, 5, 6}
• 1

Question 3

Define the complement of an event. What is it denoted by?

Answer 3

• The complement of an event A is the set of all outcomes in the sample space that are not in A.
• P(A^c) = 1 - P(A)
• P(A) = 1 - P(A^c)

Question 4

Define conditional probability.

Answer 4

• The conditional probability of B, given that A has occured, is P(B|A).
• reduces the sample space
• start by looking at the “given” event