Ch 11 – Probability & Statistics 11.4 – Compound Events

A simple event is an event that describes a single outcome. A compound event is an event made up of two or more simple events. Mutually exclusive events are events that cannot both occur in the same trial of an experiment. Probability of Mutual Exclusive Events If A and B are mutually exclusive events, then Union means “or”

A group of students is donating blood during a blood drive A group of students is donating blood during a blood drive. A student has a 9/20 probability of having type O blood and a 2/5 probability of having type A blood. Why are the events “type O” and “type A” blood mutually exclusive? B. What is the probability that a student has type O or type A blood? You can’t have type A and type O at the same time 9/20 + 2/5 = 17/20

Intersection means “and” Inclusive events are events that have one or more outcomes in common. Probability of Inclusive Events If A and B are inclusive events, then Intersection means “and”

5 6 1 3 4 Find each probability on a number cube. Rolling a 4 or an even number Rolling an odd number or a number greater than 2 P(4) = 1/6 P(even) = ½ A 4 is an even number, so the Probability of the intersection is 1/6 P(4 or an even number) = 1/6 + ½ - 1/6 = ½ 3/6 + 4/6 – 2/6 = 5/6 5 6 1 3 4

Of 1560 juniors and seniors surveyed, 840 were seniors and 630 read a daily paper. Only 215 of the paper readers were juniors. What is the probability that a student was senior or read a daily paper? 425 215 415 840 630 Paper readers seniors

Use the complement!!! Yuck! Each of 6 students randomly chooses a butterfly from a list of 8 types. What is the probability that at least 2 students choose the same butterfly? Use the complement!!! P(at least 2 students choose same) = 1 – P(all choose different) What’s the probability that 2 students choose the same butterfly? What’s the probability that 3 students choose the same butterfly? What’s the probability that 4 students choose the same butterfly? What’s the probability that 5 students choose the same butterfly? What’s the probability that 6 students choose the same butterfly? P(all choose different) = number of ways 6 students choose different butterflies total number of ways 6 students can choose butterflies . Yuck! P(at least 2 students choose same) = 1 – P(all choose different) = 1 – 0.0769 ≈ 0.9231 .

In one day, 5 different customers bought earrings from the same jewelry store. The store offers 62 different styles. Find the probability that at least 2 customers bought the same style. About .1524