D
EPARTMENT OF
E
CONOMICS
E
CON
131
A
Y
ALE
U
NIVERSITY
E
CONOMETRICS
& D
ATA
A
NALYSIS
I
F
ALL
2010
Assignment #3
Due Tuesday September 28 In Class
The same rules apply as on previous assignments. You may work with a study
group of your choice on this assignment.
However, even if you work with
others you must write up and submit your own assignment. You may do your
work by hand or in Excel, and you may hand in either handwritten answers
or typed answers. Your grade depends on (1) getting the answer right, and (2)
showing how you arrived at a correct answer. Late assignments will not be
accepted.
1. Suppose that
X
is a random variable that has a normal distribution with
mean
μ
= 5
and standard deviation
σ
= 10
. Evaluate the following probabil
ities:
(a) Prob
(
X
≥
10)
(b) Prob
(
X <
2)
(c) Prob
(6
≤
X
≤
11)
(d) Prob
((
X

10)
2
≤
12)
2. The fuel efficiency in miles per gallon of all BMW 320i’s is (approximately)
normally distributed with a mean of 25 and a standard deviation of 2.
A
dealer receives a shipment of a random sample of 320i’s (random with re
spect to m.p.g., that is) from the factory. Find the probability that
average
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 '09
 ECONOMETRICS
 Normal Distribution, Standard Deviation, Variance, Probability theory, probability density function

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