Chapter 3 Probability Additional Notes
Given two events, A , B
1. Probability of the Complement of an event:
Complement of event A is what is not in event A
So, P(complement of A) = P(A’) = 1 – P(A) [P(A) + P(A’) = 1]
2. Probability of A or B
3. Probability of A and B
Key words to look for: With replacement: Independent vs. Without replacement: Dependent
Also, if events A, B are mutually exclusive (disjoint), then they can’t be independent.
Are the events A, B mutually
exclusive(disjoint)?
P(A or B)
No
P(A)+P(B) - P(A and B)
Yes
P(A) +P(B)
Are the events A,
B independent?
P(A or B)
No
P(A)·P(B|A)
Yes
P(A)·P(B)
