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5.2 Combining Events. Objectives: By the end of this section, I will be able to… Understand how to combine events using complement, union, and intersection. Apply the Addition Rule to events in general and to mutually exclusive events in particular. Complements. What is P(4) with one die?
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5.2 Combining Events Objectives: By the end of this section, I will be able to… • Understand how to combine events using complement, union, and intersection. • Apply the Addition Rule to events in general and to mutually exclusive events in particular.
Complements • What is P(4) with one die? • What is P(not 4) with one die? • These are considered complementary events.
Complements • If one event is called Event A, the complement is called Ac.
SINGLE EVENTS • What is the p(face card) from a standard deck of cards? • What is the p(hearts) from a standard deck of cards? 12/52 13/52
COMBINING EVENTS • What is the p(face cards andhearts)? • Make a Venn Diagram
Event A = Face cards Event B = Hearts Face Cards & Hearts FACE CARDS HEARTS P(A) = 12/52 P(A) = P(B) = P(B) = 13/52 P(A and B) = P(A and B) = 3/52 SAMPLE SPACE (everything else) P(A or B) = P(A or B) = 22/52
Mutually Exclusive Events • Two events, A and B, that cannot occur at the same time. • Example: Fly a plane and drive a car at the same time (its impossible!) • KEY WORDS: OR, EITHER p(A or B) = p(A) + p(B) p(A U B) = p(A) + p(B)
Spoiled Brats • Tankle has been shopping around for a new HOT ROD!! The probability a customer will buy an JEEP is 0.23 and the probability that a customer will buy a BMW is 0.09. • What is the probability that Matt will buy EITHER of these two Cars? 0.23 + 0.09 = 0.32
CRAPS • Two dice are rolled. What is the probability that the sum of the dots is a 7 OR 11? 4,3 3,4 2,5 5,2 1,6 6,1 5,6 6,5 6/36 + 2/36= 8/36 = 0.22
OVERLAPPING Events What is the p(Ace or Hearts)? • Addition Rule: p(A or B) = p(A) + p(B) – p(A and B) SUBTRACT OUT THE OVERLAPPING PART OF THE EVENT!
CARDS • WHAT IS THE PROBABILITY OF SELECTING A RED CARDOR A KING FROM A STANDARD DECK OF CARDS? 26/52 4/52 26/52 + 4/52 – 2/52 = 28/52 = 0.53846 = 0.54
Try This One! • The probability of a guard being chosen by Coach Godfrey to start the basketball game is 0.42 and the probability that she chooses a forward is 0.34. • Three out of every fiveplayers can play both positions on Coach Godfrey’s team. • What is the probability that a player chosen to start the game is a guard OR a forward? 0.42 + 0.34 - 3/5 = 0.16