Page 81 - Probability Demystified

70 CHAPTER 4 The Multiplication Rules

Summary

When two events occur in sequence, the probability that both events occur
can be found by using one of the multiplication rules. When two events
are independent, the probability that the first event occurs does not affect
or change the probability of the second event occurring. If the events are
independent, multiplication rule I is used. When the two events are
dependent, the probability of the second event occurring is changed after
the first event occurs. If the events are dependent, multiplication rule II is
used. The key word for using the multiplication rule is ‘‘and.’’ Conditional
probability is used when additional information is known about the
probability of an event.

CHAPTER QUIZ

1. Which of the following events are dependent?

a. Tossing a coin and rolling a die
b. Rolling a die and then rolling a second die
c. Sitting in the sun all day and getting sunburned
d. Drawing a card from a deck and rolling a die
2. Three dice are rolled. What is the probability of getting three 4s?

1
a.
216
1
b.
6
1
c.
36
1
d.
18