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Practice Problems for Test 3
1.) (6.5) The distribution of the time it takes a student to complete
the fall class registration has a mean of 19 minutes, with a
standard deviation of 7.6 minutes. For a random sample of 45
students,
a)
What is the mean and the standard error of the sampling
distribution of the sample mean?
b)
What can you say about the shape of the sampling
distribution of the sample mean?
c)
What is the probability that the average of this sample
will be less than 17.5 minutes?
d)
What is the probability that the average of this sample
will be within 1 minute of the population mean.
2) (6.4) According to the National Center for Health Statistics,
22.4% of adults are smokers. Suppose a random sample of 300
adults is obtained.
a)
What is the mean and the standard error of the sampling
distribution of the sample proportion,
$
p
?
b)
What can you say about the shape of the sampling
distribution of
$
p
?
c)
Using the Empirical Rule, almost all of the sample
proportion values will be between _____ and _____.
d)
Is it likely or unlikely to observe a sample proportion of
0.32 if the population proportion really is 0.224?
3) (7.1) The mean monthly expense for entertainment per
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 Spring '08
 smith
 Standard Deviation

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