1. A level C confidence interval is
A.any interval with margin of error ± C.
B.an interval computed from sample data by a method that has probability C of producing an interval containing the true value of the parameter of interest.
C.an interval with margin of error ± C that is also correct C% of the time.
D.an interval computed from sample data by a method that guarantees that the probability the interval computed contains the parameter of interest is C.


2. I collect a random sample of size n from a population and from the data collected compute a 95% confidence interval for the mean of the population. Which of the following would produce a new confidence interval with larger width (larger margin of error) based on these same data?
A.Use a larger confidence level.
B.Use a smaller confidence level.
C.Use the same confidence level, but compute the interval n times. Approximately 5% of these intervals will be larger.
D.Nothing can guarantee absolutely that you will get a larger interval. One can only say the chance of obtaining a larger interval is 0.05.


3.
An agricultural researcher plants twenty-five plots with a new variety of corn. The average yield for these plots is J = 150 bushels per acre. Assume that the yield per acre for the new variety of corn follows a normal distribution with unknown mean m and standard deviation s = 10 bushels per acre.
R-1 Ref 6-1

A 90% confidence interval for m is
A.150 ± 2.00.
B.150 ± 3.29.
C.150 ± 3.92.
D.150 ± 32.90.



4.
An agricultural researcher plants twenty-five plots with a new variety of corn. The average yield for these plots is J = 150 bushels per acre. Assume that the yield per acre for the new variety of corn follows a normal distribution with unknown mean m and standard deviation s = 10 bushels per acre.
R-1 Ref 6-1

Which of the following would produce a confidence interval with a smaller margin of error than the 90% confidence interval you computed above?
A.Plant only 5 plots rather than 25, since 5 are easier to manage and control.
B.Plant 100 plots rather than 25.
C.Compute a 99% confidence interval rather than a 90% confidence interval. The increase in confidence indicates that we have a better interval.
D.None of the above.



5. You plan to construct a confidence interval for the mean m of a normal population with (known) standard deviation s. Which of the following will reduce the size of the margin of error?
A.Use a lower level of confidence
B.Increase the sample size
C.Reduce s
D.All of the above.


6. To assess the accuracy of a laboratory scale, a standard weight that is known to weigh 1 gram is repeatedly weighed a total of n times and the mean J of the weighings is computed. Suppose the scale readings are normally distributed with unknown mean m and standard deviation s = 0.01 g. How large should n be so that a 95% confidence interval for m has a margin of error of ± 0.0001?
A.100
B.196
C.10000
D.38416


7.

The distribution of a critical dimension of the crankshaft produced by a manufacturing plant for a certain type of automobile engine is normal with mean m and standard deviation s = 0.02 mm. Suppose I select a simple random sample of four of the crankshafts produced by the plant and measure this critical dimension. The results of these four measurements are


200.01

199.98

200.00

200.01


Based on these data, a 90% confidence interval for m is


A.200.00 ± 0.0082.
B.200.00 ± 0.0115.
C.200.00 ± 0.0165.
D.200.00 ± 0.0196.


8. The mean area m of the several thousand apartments in a new development is advertised to be 1250 square feet. A tenant group thinks that the apartments are smaller than advertised. They hire an engineer to measure a sample of apartments to test their suspicion. The appropriate null and alternative hypotheses, H0 and Ha, for m
A.are H0: m = 1250 and Ha: m ¹ 1250.
B.are H0: m = 1250 and Ha: m < 1250.
C.are H0: m = 1250 and Ha: m > 1250.
D.cannot be specified without knowing the size of the sample used by the engineer.


9. In a statistical test of hypotheses, we say the data are statistically significant at level a if
A.a = 0.05.
B.a is small.
C.the P-value is less than a.
D.the P-value is larger than a.


10.

The nicotine content in cigarettes of a certain brand is normally distributed with mean (in milligrams) m and standard deviation s = 0.1. The brand advertises that the mean nicotine content of their cigarettes is 1.5, but measurements on a random sample of 100 cigarettes of this brand gave a mean of J = 1.53. Is this evidence that the mean nicotine content is actually higher than advertised? To answer this question, test the hypotheses


H0: m = 1.5, Ha: m > 1.5


at significance level a = 0.05. You conclude


A.that H0 should be rejected.
B.that H0 should not be rejected.
C.that Ha should be rejected.
D.there is a 5% chance that the null hypothesis is true.


11. The weights of three adult males are (in pounds) 160, 215, and 195. The standard error of the mean of these three weights is
A.190.00.
B.27.84.
C.22.73.
D.16.07.


12.

An SRS of 100 postal employees found that the average time these employees had worked for the postal service was J = 7 years with standard deviation s = 2 years. Assume the distribution of the time the population of employees have worked for the postal service is approximately normal with mean m. Are these data evidence that m has changed from the value of 7.5 years of 20 years ago? To make this determination we test the hypotheses

H0: m = 7.5, Ha: m ¹ 7.5


using the one-sample t test.

R-2 Ref 7-1

The appropriate degrees of freedom for this test are
A.9.
B.10.
C.99.
D.100.



13.

An SRS of 100 postal employees found that the average time these employees had worked for the postal service was J = 7 years with standard deviation s = 2 years. Assume the distribution of the time the population of employees have worked for the postal service is approximately normal with mean m. Are these data evidence that m has changed from the value of 7.5 years of 20 years ago? To make this determination we test the hypotheses

H0: m = 7.5, Ha: m ¹ 7.5


using the one-sample t test.

R-2 Ref 7-1

The P-value for the one-sample t test is
A.larger than 0.10.
B.between 0.10 and 0.05.
C.between 0.05 and 0.01.
D.below 0.01.



14.

An SRS of 100 postal employees found that the average time these employees had worked for the postal service was J = 7 years with standard deviation s = 2 years. Assume the distribution of the time the population of employees have worked for the postal service is approximately normal with mean m. Are these data evidence that m has changed from the value of 7.5 years of 20 years ago? To make this determination we test the hypotheses

H0: m = 7.5, Ha: m ¹ 7.5


using the one-sample t test.

R-2 Ref 7-1

A 95% confidence interval for the mean time m the population of postal service employees have spent with the postal service is
A.7 ± 2.
B.7 ± 1.984.
C.7 ± 0.4.
D.7 ± 0.2.




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