ECON 2843
Problem Set 6
1.
Problem 7.8 in Newbold on p. 233
Candidates for employment at a city fire department are required to take a written
aptitude test.
Scores on this test are normally distributed with mean 280 and stand
deviation 60.
A random sample of nine test scores was taken.
a.
What is the standard error of the sample mean score?
b.
What is the probability that the sample mean score is less than 270?
c.
What is the probability that the sample mean score is more than 250?
2.
Problem 7.11 in Newbold on p. 234.
Assume that the standard deviation of monthly rents paid by students in a particular town
is $40.
A random sample of 100 students was taken to estimate the mean monthly rent
paid by the whole student population.
a.
What is the standard error of the sample mean monthly rent?
b.
What is the probability that the sample mean exceeds the population mena
by more than $5?
c.
What is the probability that the sample mean is more than $4 below the
population mean?
d.
What is the probability that the sample mean differs from the population
mean by more than $3?
3.
Problem 7.15 in Newbold on p. 234.
The number of hours spent studying by students on a large campus in the week before
final exams follows a normal distribution with standard deviation 8.4 hours.
A random
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 Spring '08
 HUDGINS
 Normal Distribution, Standard Deviation, Variance, Newbold

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