Mutually Exclusive Events
Hipster Venn Diagram
What if… We wanted the probability of event A happening OR event B happening? To answer this we first must define a few things
Mutually exclusive events are… two events that have NO COMMON ELEMENTS (they cannot both occur at the same time). Examples: Drawing an ace, or a face card Rolling doubles, or a total of 7 on two dice Key terms: or, no common element
Mutually Exclusive Events (A Visual)
To find P(A U B) for two mutually exclusive events A and B… you ADD the probabilities P(AUB) = P(A) + P(B)
Mutually Exclusive Example A pair of dice is rolled. What is the probability that the sum of the numbers rolled is either 7 OR 11?
Non-Mutually Exclusive Events Two events, A and B are Not Mutually Exclusive, if they share a common element. Examples: Drawing a king or a face card Rolling doubles or a total of 10 with some dice
Non-Mutually Exclusive Events The probability P(AUB) of non-mutually exclusive events is given by… P(AUB) = P(A) + P(B) – P(A∩B) But why subtract the intersection?
Non-Mutually Exclusive Events (A Visual) The intersection is added TWICE because of the overlap. So we subtract it ONCE. P(AUB) = P(A) + P(B) – P(A∩B)
Non-Mutually Exclusive Example A pair of dice is rolled. What is the probability doubles are rolled OR a total of 10 is rolled?
Homework P. 42 #1 - 7, 9a, 10, 11, 14