294 / 762
294
Chapter 7: Probability
= 0.31.
The Addition Rule
A more generalized rule for the union of two events is given next.
Rule 7:
For any two events
A
and
B
, the probability of their union is given
by
This is usually called the
Addition Rule
of probability. The Venn diagram
in
Figure 7-16
depicts this rule. The striped area represents
P
(
A
B
).
Figure 7-16:
Venn diagram depicting the Addition Rule
Example 7-19:
In a sample of 100 college students, 73 said they own a
smart phone, 20 said they own an i-Pad, and 10 said they own both a smart
phone and an i-Pad. What is the probability of a student having a smart
phone, or an i-Pad, or both a smart phone and an i-pad?