Probability Any event occurring as a result of a random experiment will usually be denoted by a capital letter from the early part of the alphabet. e.g. When a die is thrown, it is possible to have the following events A = throwing an even number B = throwing a multiple of 3 If A does not occur, it is denoted by A’. ThereforeA’ = not throwing an even number B’ =not throwing a multiple of 3

Combined Events For any two events A and B a)the event that “A or B or both occur” is called the union of A and B and will be written as A ∪ B b) the event that “both A and B will occur” is called the intersection of A and B and will be written as A ∩ B

Mutually exclusive events It is said that two events which cannot occur at the same time are mutually exclusive. e.g. 3 coins are tossed. A is the event that only two heads are thrown. B is the event that all three coins will have the same result. A and B are mutually exclusive because it is impossible for A and B to occur together. Exercise 3.2 Mathematics Statistics Unit S1 - WJEC