Page 210 - Math Course 3 (Book 2)

Probability of Compound Events
Mo. 12

Lesson 7 dependent events

When the outcome of one event affects the
outcome of another event, the events are
dependent events.
KEY CONCEPTS:
Drawing a marble from a bag, not returning it, then
1. Find the probability of two independent drawing a second marble are dependent events
events or dependent events. because the drawing of the second marble is
2. Find the probability of two mutually dependent on the drawing of the first marble.
exclusive or inclusive events.

Key Concept
MO. 12 - L7a

Independent and Dependent Probability of Independent Events

Events
Words If two events, A and B, are independent,
then the probability of both events oc-
Vocabulary A-Z curring is the product of the probability
of A and the probability of B.
Let us learn some vocabulary
Symbols P(A and B) = P(A) • P(B)

simple event Model

A single event, like rain in Los Angeles, is called a
P
simple event. A (A and B) B

Saturday Forecast: Rain Likely

Los Angeles
80%
Probability of Dependent Events
compound events
Suppose you wanted to determine the probability Words If two events, A and B, are dependent,
that it will rain in both Chicago and Los Angeles. then the probability of both events
This is an example of a compound event, which is occurring is the product of the
made up of two or more simple events. probability of A and the probability of B
after A occurs.
Saturday Forecast: Rain Likely
Symbols P(A and B) = P(A) • P(B following A)

Chicago
40%

Los Angeles
80%

independent events
The weather in Chicago does not affect the weather
in Los Angeles. These two events are called inde-
pendent events because the outcome of one event
does not affect the outcome of the other.
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