3.1 Terminology

A and B are events.

P(S) = 1 where S is the sample space

0 ≤ P(A) ≤ 1

P(A|B) = $\frac{P\text{(}A\text{AND}B\text{)}}{P\text{(}B\text{)}}$

3.2 Independent and Mutually Exclusive Events

If A and B are independent, P(A AND B) = P(A)P(B), P(A|B) = P(A), and P(B|A) = P(B).

If A and B are mutually exclusive, P(A OR B) = P(A) + P(B) and P(A AND B) = 0.

3.3 Two Basic Rules of Probability

The multiplication rule—P(A AND B) = P(A|B)P(B)

The addition rule—P(A OR B) = P(A) + P(B) − P(A AND B)