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EXAM 2 REVIEW
(answers will be posted on http://faculty.deanza.edu/plumkathryn
a couple days before the
exam)
Round probabilities to 4 decimal places.
Round any other answers to 2 decimal places.
1.
Suppose that the speed of trains over a certain railroad bridge varies between 42 and 58 miles per hour
and is uniformly distributed.
a.
Define the random variable X, in words:
X =
b.
X ~
c.
µ =
d.
σ =
e.
f(x) =
f.
Find the probability that the speed of a train over the bridge is at least 53 miles per hour.
g.
Find the probability that the speed of a train over the bridge is between 47 and 53 miles per hour.
h.
30% of the trains travel at least how fast over the bridge?
i.
Find the probability that the speed of a train over the bridge is less than 50 miles per hour GIVEN it
is traveling less than 55 miles per hours.
2.
The U. S. Census in the year 2000 gathered data
about the people living in owner occupied
housing units (such as houses and condominiums).
The census data shows that the number of people
per
household follows the probability distribution
shown:
Household Size for
OwnerOccupied Housing Units
X = number of people
in household
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 Fall '11
 Plum
 Statistics

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