NATALIA SIVACKOVA Introduction to Probability

Equally Likely Events Coin toss example: Probability of result is ½ Dice example: Probability of result is 1/6 For nth term Probability = 1/n

Not Equally Likely Events Bag of marbles 4 blue 5 green 6 red Probability of picking blue? 4/15

General Formula The bag is U n(U) = 15 Blue marbles form a subset A U Probability of picking a member of A is P(A) P(A) = n(A)/n(U)

Probability of a Complementary Event Sock drawer contains 53 socks 13 are single socks 40 are in a pair Probability of single sock: n(S)/n(U) = 13/53 Probability of a sock from a pair: n(S)/n(U) = 40/53 P(S) + P(S) = 53/53 = 1 Generalized formula for all subsets: P(S) = 1 – P(S) S S = U

Cont. When an event is certain it has a probability of 1 When an event is impossible it has a probability of 0 (e.g. of an impossible event) S S = (You cannot pick a sock that is both single and part of a pair)