Probability measures how likely an event is: P(E) = number of favourable outcomes ÷ total number of equally likely outcomes.
1Rules
0 ≤ P(E) ≤ 1; P(not E) = 1 − P(E)
P(A or B) = P(A) + P(B) − P(A and B)
Independent events: P(A and B) = P(A) × P(B)
2Standard sample spaces
n coins: 2ⁿ outcomes; two dice: 36 outcomes
A pack of 52 cards has 4 suits of 13; 12 face cards (J, Q, K); 26 red and 26 black cards
Drawing r items from n: ⁿCᵣ outcomes