Statistics Exam 2
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June 4, 2008
your intention to abide by the honor pledge:
PID:
This exam contains
fifteen
short answer questions
(
worth 4 points each
)
and
three
long answer questions
(
worth 15 points each
)
.
Please answer in the space provided; if
you need more room, indicate clearly that the answer is continued on the back of the
page.
In all problems where you need to make a calculation, simplify your answer as
much as possible.
Show your work clearly to be eligible for partial credit.
Some PDFs:
Some probabilities:
f
(
x
)
=
1
2
!"
2
e
#
(
X
#
μ
)
2
"
2
P
[
x
!
a
]
=
e
"
#
a
f
(
x
)
=
1
u
!
!
P
[
X
]
=
x
e
!
X
!
f
(
x
)
=
!
e
"
x
P
[
X
]
=
N
!
X
!(
N
!
X
)!
p
X
(1
!
p
)
N
!
X
Short Questions
(
4 points apiece
)
1.
X
is a random variable with a continuous distribution.
Its probability density
function is
f
(
x
)
, and its cumulative density function is
F
(
x
)
.
What is the
relationship between these functions?
2.
According to the Center for Disease Control, the average height of a man in the
U.S. is
69
inches; the standard deviation is
3
.
If this variable has a normal
distribution, how would we write its probability density function?
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View Full DocumentEcon 400 Midterm 2, page 2 of 8.
3.
You collect data from 100 students on the number of hours they spend on the
internet in a typical week.
The average of this sample is
10
.
2
, with a standard
deviation of
4
.
8
.
Construct a 95
%
confidence interval for the population mean.
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 Spring '08
 turchi
 Normal Distribution, Probability theory, probability density function

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