Practice Questions 2
ECO 329
1.
The finishing process on new furniture leaves slight blemishes.
The table shown below
displays a manager’s probability assessment of the number of blemishes in the finish of
new furniture.
Number of Blemishes
0
1
2
3
4
5
Probability
0.34
0.25
0.19
0.11
0.07
0.04
a.
Let event
A
be that there are more than three blemishes and let event
B
be that there are
four or fewer blemishes.
Which of the following statements is true?
A)
P
(
A B
I
) = 0.18.
B)
P
(
A B
U
) = 0.07.
C)
Events
A
and
B
are collectively exhaustive.
D)
Events
A
and
B
are mutually exclusive.
b.
Let event
A
be that there are more than two blemishes and let event
B
be that there are
four or fewer blemishes.
Which of the following statements is true?
A)
P
(
A B
I
) = 0.18.
B)
P
(
A B
U
) = 0.07.
C)
P
(
A
) = 0.58.
D)
P
(
B
) = 0.89.
2.
The probability that an employee at a company uses illegal drugs is 0.08.
The probability
than an employee is male is 0.55.
Assuming that these events are independent, what is
the probability that a randomly chosen employee is a male drug user?
A)
0.742
B)
0.145
C)
0.044
D)
0.006
3.
Fred’s Surfboard Shop makes surfboards by hand.
The number of surfboards that Fred
makes during a week depends on the wave conditions.
Fred has estimated the following
probabilities for surfboard production for the next week.
Number of Surfboards
5
6
7
8
9
10
Probability
0.13
0.22
0.31
0.17
0.13
0.04
Let
A
be the event that Fred produces more than seven surfboards.
Let
B
be the event that Fred
produces exactly six surfboards.
a.
What is the probability of event
A
?
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Are events A and B collectively exhaustive? Why?
c.
What is the probability of the complement of
A
?
d.
What is the probability of the intersection of events
A
and
B
? Why?
4.
In a recent survey about US policy in Iraq, 62 % of the respondents said that they support
US policy in Iraq. Females comprised 53% of the sample, and of the females, 46%
supported US policy in Iraq.
A person is selected at random.
a.
What is the probability that the person we select is female and support US policy
in Iraq?
b.
Are the events “does not support US policy in Iraq” and “female” statistically
independent?
Why or why not?
c.
What is the probability that the person we select is male?
d.
What is the probability that the person we select does not support US policy in
Iraq?
e.
What is the probability that the person we select is female and doe not support
US policy in Iraq?
f.
What is the probability that the person we select is male and does support US
policy in Iraq?
g.
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 Spring '08
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