Question 1

The t distribution should be used whenever _____.

Accepted Answer

A)   the sample size is less than 30
B)   the sample standard deviation is used to estimate the population standard deviation
C)   the population is not normally distributed
D)   None of the answers is correct.E) B) and D)
F) A) and B)

Question 2

For the interval estimation of μ when σ is assumed known, the proper distribution to use is the_____.

Accepted Answer

A)   standard normal distribution
B)   t distribution with n degrees of freedom
C)   t distribution with n − 1 degrees of freedom
D)   t distribution with n − 2 degrees of freedomE) A) and D)
F) All of the above

Question 3

A 95% confidence interval for a population mean is determined to be 100 to 120. If the confidence coefficient is reduced to .90, the interval for μ _____.

Accepted Answer

A)   becomes narrower
B)   becomes wider
C)   does not change
D)   becomes .1E) A) and B)
F) None of the above

Question 4

A random sample of 25 statistics examinations was selected. The average score in the sample was 76 with a variance of 144. Assuming the scores are normally distributed, the 99% confidence interval for the population average examination score is _____.

Accepted Answer

A)   70.02 to 81.98
B)   69.82 to 82.18
C)   70.06 to 81.94
D)   69.29 to 82.71E) A) and B)
F) None of the above

Question 5

An auto manufacturer wants to estimate the annual income of owners of a particular model of automobile. A random sample of 200 current owners is selected. The population standard deviation is known. Which Excel function would NOT be appropriate to use to construct a confidence interval estimate?

Accepted Answer

A)   NORM.S.INV
B)   COUNTIF
C)   AVERAGE
D)   STDEVE) None of the above
F) All of the above

Question 6

To estimate a population mean, the sample size needed to provide a margin of error of 2 or less with a .95 probability when the population standard deviation equals 11 is _____.

Accepted Answer

A)   10
B)   11
C)   116
D)   117E) B) and C)
F) C) and D)

Question 7

It is known that the variance of a population equals 1,936. A random sample of 121 has been selected from the population. There is a .95 probability that the sample mean will provide a margin of error of _____.

Accepted Answer

A)   7.84 or less
B)   31.36 or less
C)   344.96 or less
D)   1,936 or lessE) B) and D)
F) None of the above

Question 8

From a population that is normally distributed with an unknown standard deviation, a sample of 25 elements is selected. For the interval estimation of μ, the proper distribution to use is the _____.

Accepted Answer

A)   standard normal distribution
B)   z distribution
C)   t distribution with 26 degrees of freedom
D)   t distribution with 24 degrees of freedomE) None of the above
F) B) and C)

Question 9

In developing an interval estimate of the population mean, if the population standard deviation is unknown _____.

Accepted Answer

A)   it is impossible to develop an interval estimate
B)   a sample proportion can be used
C)   the sample standard deviation and t distribution can be used
D)   None of the answers is correct.E) A) and C)
F) A) and B)

Question 10

We can reduce the margin of error in an interval estimate of p by doing any of the following EXCEPT _____.

Accepted Answer

A)   increasing the sample size
B)   using a planning value p* closer to .5
C)   increasing the level of significance
D)   reducing the confidence coefficientE) All of the above
F) B) and D)

Question 11

In determining an interval estimate of a population mean when ? is unknown, we use a t distribution with _____ degrees of freedom.

Accepted Answer

A)    n−1\sqrt { n - 1 }n−1c-2.7,0,-7.17,-2.7,-13.5,-8c-5.8,-5.3,-9.5,-10,-9.5,-14c0,-2,0.3,-3.3,1,-4c1.3,-2.7,23.83,-20.7,67.5,-54c44.2,-33.3,65.8,-50.3,66.5,-51c1.3,-1.3,3,-2,5,-2c4.7,0,8.7,3.3,12,10s173,378,173,378c0.7,0,35.3,-71,104,-213c68.7,-142,137.5,-285,206.5,-429c69,-144,104.5,-217.7,106.5,-221l0 -0c5.3,-9.3,12,-14,20,-14H400000v40H845.2724s-225.272,467,-225.272,467s-235,486,-235,486c-2.7,4.7,-9,7,-19,7c-6,0,-10,-1,-12,-3s-194,-422,-194,-422s-65,47,-65,47zM834 80h400000v40h-400000z'/>​ 
B)    n\sqrt { n }nc-2.7,0,-7.17,-2.7,-13.5,-8c-5.8,-5.3,-9.5,-10,-9.5,-14c0,-2,0.3,-3.3,1,-4c1.3,-2.7,23.83,-20.7,67.5,-54c44.2,-33.3,65.8,-50.3,66.5,-51c1.3,-1.3,3,-2,5,-2c4.7,0,8.7,3.3,12,10s173,378,173,378c0.7,0,35.3,-71,104,-213c68.7,-142,137.5,-285,206.5,-429c69,-144,104.5,-217.7,106.5,-221l0 -0c5.3,-9.3,12,-14,20,-14H400000v40H845.2724s-225.272,467,-225.272,467s-235,486,-235,486c-2.7,4.7,-9,7,-19,7c-6,0,-10,-1,-12,-3s-194,-422,-194,-422s-65,47,-65,47zM834 80h400000v40h-400000z'/>​ 
C)   n ? 1
D)   n E) B) and C)
F) All of the above

Question 12

From a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for μ. Which of the following statements is true?

Accepted Answer

A)   The standard normal distribution can be used.
B)   The t distribution with 50 degrees of freedom must be used.
C)   The t distribution with 49 degrees of freedom must be used.
D)   The sample size must be increased in order to develop an interval estimate.E) None of the above
F) A) and D)

Question 13

As the sample size increases, the margin of error _____.

Accepted Answer

A)   increases
B)   decreases
C)   stays the same
D)   None of the answers is correct.E) B) and D)
F) B) and C)

Question 14

We can use the normal distribution to make confidence interval estimates for the population proportion, p, when _____.

Accepted Answer

A)   np ≥ 5
B)   n(1 − p)  ≥ 5
C)   p has a normal distribution
D)   np ≥ 5 and n(1 − p)  ≥ 5E) A) and C)
F) B) and C)

Question 15

The general form of an interval estimate of a population mean or population proportion is the _____ plus or minus the _____.

Accepted Answer

A)   population mean, standard error
B)   level of significance, degrees of freedom
C)   point estimate, margin of error
D)   planning value, confidence coefficientE) A) and D)
F) All of the above

Question 16

The probability that the interval estimation procedure will generate an interval that contains the actual value of the population parameter being estimated is the _____.

Accepted Answer

A)   level of significance
B)   confidence level
C)   confidence coefficient
D)   error factorE) A) and D)
F) None of the above

Question 17

A random sample of 36 students at a community college showed an average age of 25 years. Assume the ages of all students at the college are normally distributed with a standard deviation of 1.8 years. The 98% confidence interval for the average age of all students at this college is _____.

Accepted Answer

A)   24.301 to 25.699
B)   24.385 to 25.615
C)   23.200 to 26.800
D)   23.236 to 26.764E) C) and D)
F) B) and C)

Question 18

A random sample of 36 students at a community college showed an average age of 25 years. Assume the ages of all students at the college are normally distributed with a standard deviation of 1.8 years. The 98% confidence interval for the average age of all students at this college is _____.

Accepted Answer

A)   24.301 to 25.699
B)   24.385 to 25.615
C)   23.200 to 26.800
D)   23.236 to 26.764E) A) and C)
F) C) and D)

Question 19

Using α = .04, a confidence interval for a population proportion is determined to be .65 to .75. If the level of significance is decreased, the interval for the population proportion _____.

Accepted Answer

A)   becomes narrower
B)   becomes wider
C)   does not change
D)   Not enough information is provided to answer this question.E) A) and C)
F) A) and D)

Question 20

From a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for μ. Which of the following statements is true?

Accepted Answer

A)   The standard normal distribution can be used.
B)   The t distribution with 50 degrees of freedom must be used.
C)   The t distribution with 49 degrees of freedom must be used.
D)   The sample size must be increased in order to develop an interval estimate.E) B) and C)
F) A) and B)

Exam 8: Interval Estimation

We can use the normal distribution to make confidence interval estimates for the population proportion, p, when _____.

Correct AnswerverifiedShow Answer

The probability that the interval estimation procedure will generate an interval that contains the actual value of the population parameter being estimated is the _____.

Correct AnswerverifiedShow Answer

A 95% confidence interval for a population mean is determined to be 100 to 120. If the confidence coefficient is reduced to .90, the interval for μ _____.

Correct AnswerverifiedShow Answer

From a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for μ. Which of the following statements is true?

Correct AnswerverifiedShow Answer

The general form of an interval estimate of a population mean or population proportion is the _____ plus or minus the _____.

Correct AnswerverifiedShow Answer

In developing an interval estimate of the population mean, if the population standard deviation is unknown _____.

Correct AnswerverifiedShow Answer

An auto manufacturer wants to estimate the annual income of owners of a particular model of automobile. A random sample of 200 current owners is selected. The population standard deviation is known. Which Excel function would NOT be appropriate to use to construct a confidence interval estimate?

Correct AnswerverifiedShow Answer

We can reduce the margin of error in an interval estimate of p by doing any of the following EXCEPT _____.

Correct AnswerverifiedShow Answer

A random sample of 36 students at a community college showed an average age of 25 years. Assume the ages of all students at the college are normally distributed with a standard deviation of 1.8 years. The 98% confidence interval for the average age of all students at this college is _____.

Correct AnswerverifiedShow Answer

From a population that is normally distributed with an unknown standard deviation, a sample of 25 elements is selected. For the interval estimation of μ, the proper distribution to use is the _____.

Correct AnswerverifiedShow Answer

In determining an interval estimate of a population mean when ? is unknown, we use a t distribution with _____ degrees of freedom.

Correct AnswerverifiedShow Answer

From a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for μ. Which of the following statements is true?

Correct AnswerverifiedShow Answer

The t distribution should be used whenever _____.

Correct AnswerverifiedShow Answer

A random sample of 25 statistics examinations was selected. The average score in the sample was 76 with a variance of 144. Assuming the scores are normally distributed, the 99% confidence interval for the population average examination score is _____.

Correct AnswerverifiedShow Answer

A random sample of 36 students at a community college showed an average age of 25 years. Assume the ages of all students at the college are normally distributed with a standard deviation of 1.8 years. The 98% confidence interval for the average age of all students at this college is _____.

Correct AnswerverifiedShow Answer

It is known that the variance of a population equals 1,936. A random sample of 121 has been selected from the population. There is a .95 probability that the sample mean will provide a margin of error of _____.

Correct AnswerverifiedShow Answer

Using α = .04, a confidence interval for a population proportion is determined to be .65 to .75. If the level of significance is decreased, the interval for the population proportion _____.

Correct AnswerverifiedShow Answer

As the sample size increases, the margin of error _____.

Correct AnswerverifiedShow Answer

To estimate a population mean, the sample size needed to provide a margin of error of 2 or less with a .95 probability when the population standard deviation equals 11 is _____.

Correct AnswerverifiedShow Answer

For the interval estimation of μ when σ is assumed known, the proper distribution to use is the_____.

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

The general form of an interval estimate of a population mean or population proportion is the _ plus or minus the _.

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified