Question 1

How is the efficiency of estimators defined?

Accepted Answer

A) An estimator is efficient if its expected value equals the estimated population parameter. 
B) An efficient estimator approaches the estimated population parameter as the sample size grows larger. 
C) An estimator is efficient if it always gives the correct value of the estimated population parameter. 
D) An unbiased estimator is efficient if its standard error is lower than that of other estimators of the estimated population parameter. 
A) An estimator is efficient if its expected value equals the estimated population parameter. 
B) An efficient estimator approaches the estimated population parameter as the sample size grows larger. 
C) An estimator is efficient if it always gives the correct value of the estimated population parameter. 
D) An unbiased estimator is efficient if its standard error is lower than that of other estimators of the estimated population parameter.

Question 2

The t distribution has broader tails than the z distribution.

Accepted Answer

A) True 
 B)False

Question 3

Given a sample mean of 12.5-drawn from a normal population,a sample of size 25,and a sample variance of 2.4-find a 99% confidence interval for the population mean.

Accepted Answer

A) [11.7019,13.2981] 
B) [11.1574,13.8426] 
C) [11.6334,13.3666] 
D) [11.7279,13.2721] 
A) [11.7019,13.2981] 
B) [11.1574,13.8426] 
C) [11.6334,13.3666] 
D) [11.7279,13.2721]

Question 4

Bobby does not want to be late to work again.He drives to work every morning from Oakland to San Francisco and crossing the Bay Bridge seems to take forever.He times himself crossing the bridge for seven consecutive mornings,with the resulting times: 22.34,27.54,15.26,13.56,18.57,21.22,and 19.08 minutes.Construct a 99% confidence interval from those times.

Accepted Answer

The answer of Bobby does not want to be late...

Question 5

A sample of holiday shoppers is taken randomly from a local mall.Forty-nine shoppers were selected and asked what their average spending on gifts would be during the entire holiday season.The point estimate of the population mean was calculated as $550 and the sample standard deviation was calculated as $92.
A)Construct a 95% confidence interval of the population mean spending.
B)Explain how the central limit theorem is used in constructing this interval.

Accepted Answer

[523.5697,576.4303].The condit

Question 6

Exhibit 8.4.According to a report in USA Today (February 1,2012),more and more parents are helping their young adult children get homes.Suppose 8 persons in a random sample of 40 young adults who recently purchased a home in Kentucky got help from their parents.You have been asked to construct a 95% confidence interval for the population proportion of all young adults in Kentucky who got help from their parents. Refer to Exhibit 8.4.What is the margin of error for a 95% confidence interval for the population proportion?

Accepted Answer

A) 1.645(0.0040) 
B) 1.645(0.0632) 
C) 1.96(0.0040) 
D) 1.96(0.0632) 
A) 1.645(0.0040) 
B) 1.645(0.0632) 
C) 1.96(0.0040) 
D) 1.96(0.0632)

Question 7

The height of high school basketball players is known to be normally distributed with a standard deviation of 1.75 inches.In a random sample of eight high school basketball players,the height (in inches)is recorded as 75,82,68,74,78,70,77,and 76.Construct a 95% confidence interval on the average height of all high school basketball players.

Accepted Answer

[73.7873,76.2127];95% of inter

Question 8

What is the minimum sample size required to estimate a population mean with 90% confidence when the desired margin of error is D = 1.25? The standard deviation in a preselected sample is 8.5.

Accepted Answer

A) n = 76 
B) n = 125 
C) n = 126 
D) n = 190 
A) n = 76 
B) n = 125 
C) n = 126 
D) n = 190

Question 9

A company manager thinks he is overpaying for fertilizer at $174 per ton.To find out,he collects fertilizer prices per ton from five distributors.Construct a 90% confidence interval from his results: 128,140,170,166,and 156.

Accepted Answer

The answer of A company manager thinks he is overpaying...

Question 10

How do the t and z distributions differ?

Accepted Answer

A) There is no difference between the t and z distributions. 
B) The z distribution has broader tails (it is flatter around zero). 
C) The t distribution has broader tails (it is flatter around zero). 
D) The z distribution has asymptotic tails,while the t distribution does not. 
A) There is no difference between the t and z distributions. 
B) The z distribution has broader tails (it is flatter around zero). 
C) The t distribution has broader tails (it is flatter around zero). 
D) The z distribution has asymptotic tails,while the t distribution does not.

Question 11

A medical engineering company creates x-ray machines.The machines the company sold in 1995 were expected to last six years before breaking.To test how long the machines actually lasted,the company took a simple random sample of six machines.The company got the following results (in years)for how long the x-ray machines lasted: 8,6,7,9,5,and 7.Assume the distribution of the longevity of x-ray machines is normally distributed.Construct a 98% confidence interval for the average longevity of x-ray machines.

Accepted Answer

The answer of A medical engineering company creates x-ray machines.The...

Question 12

A sample of a given size is used to construct a 95% confidence interval for the population mean with a known population standard deviation.If a bigger sample had been used instead,then the 95% confidence interval would have been _______ and the probability of making an error would have been ________.

Accepted Answer

A) Wider,smaller 
B) Narrower,smaller 
C) Wider,unchanged 
D) Narrower,unchanged 
A) Wider,smaller 
B) Narrower,smaller 
C) Wider,unchanged 
D) Narrower,unchanged

Question 13

A job candidate with an offer from a prominent investment bank wanted to estimate how many hours she would have to work per week during her first year at the bank.She took a sample of six first-year analysts,asking how many hours they worked in the last week.Construct a 95% confidence interval with her results: 64,82,74,73,78,and 87 hours.

Accepted Answer

The answer of A job candidate with an offer from...

Question 14

The minimum sample size n required to estimate a population mean with 95% confidence and the desired margin of error 1.5 was found to be 198.Which of the following is the approximate value of the assumed estimate of the population standard deviation?

Accepted Answer

A) 10.7688 
B) 12.8309 
C) 115.9671 
D) 164.6326 
A) 10.7688 
B) 12.8309 
C) 115.9671 
D) 164.6326

Question 15

We draw a random sample of size 25 from the normal population with the variance 2.4.If the sample mean is 12.5,what is a 99% confidence interval for the population mean?

Accepted Answer

A) [11.2600,13.7400] 
B) [11.3835,13.6165] 
C) [11.7019,13.2981] 
D) [11.7793,13.2207] 
A) [11.2600,13.7400] 
B) [11.3835,13.6165] 
C) [11.7019,13.2981] 
D) [11.7793,13.2207]

Question 16

What conditions are required by the central limit theorem before a confidence interval of the population mean may be created?

Accepted Answer

A) The underlying population must be normally distributed. 
B) The underlying population must be normally distributed if the sample size is 30 or more. 
C) The underlying population need not be normally distributed if the sample size is 30 or more. 
D) The underlying population need not be normally distributed if the population standard deviation is known. 
A) The underlying population must be normally distributed. 
B) The underlying population must be normally distributed if the sample size is 30 or more. 
C) The underlying population need not be normally distributed if the sample size is 30 or more. 
D) The underlying population need not be normally distributed if the population standard deviation is known.

Question 17

Construct a 90% confidence interval on the population proportion for the support of candidate A in the following mayoral election.Candidate A is facing two opposing candidates.In a recent poll of 300 residents,153 supported her.

Accepted Answer

A) [0.4534,0.5666] 
B) [0.4625,0.5575] 
C) [0.5086,0.5114] 
D) [0.5090,0.5110] 
A) [0.4534,0.5666] 
B) [0.4625,0.5575] 
C) [0.5086,0.5114] 
D) [0.5090,0.5110]

Question 18

The t distribution consists of a family of distributions where the actual shape of each one depends on the degrees of freedom,df.For lower values of df,the t distribution is similar to the z distribution.

Accepted Answer

A) True 
 B)False

Question 19

The confidence intervals for the population proportion are generally based on ___________.

Accepted Answer

A) The z distribution 
B) The t distribution 
C) The z distribution when the sample size is very small 
D) The t distribution when the population standard deviation is not known 
A) The z distribution 
B) The t distribution 
C) The z distribution when the sample size is very small 
D) The t distribution when the population standard deviation is not known

Question 20

Exhibit 8-3.Professors of Accountancy are in high demand at American universities.A random sample of 28 new accounting professors found the average salary was 135 thousand dollars with a standard deviation of 16 thousand dollars.Assume the distribution is normally distributed. Refer to Exhibit 8-3.Construct a 90% confidence interval for the salary of new accounting professors.Answers are in thousands of dollars.

Accepted Answer

A) [107.7520,162.2480] 
B) [129.8506,140.1494] 
C) [130.0260,139.9740] 
D) [131.0268,138.9732] 
A) [107.7520,162.2480] 
B) [129.8506,140.1494] 
C) [130.0260,139.9740] 
D) [131.0268,138.9732]

How is the efficiency of estimators defined?

The t distribution has broader tails than the z distribution.

Given a sample mean of 12.5-drawn from a normal population,a sample of size 25,and a sample variance of 2.4-find a 99% confidence interval for the population mean.

What is the minimum sample size required to estimate a population mean with 90% confidence when the desired margin of error is D = 1.25? The standard deviation in a preselected sample is 8.5.

A company manager thinks he is overpaying for fertilizer at $174 per ton.To find out,he collects fertilizer prices per ton from five distributors.Construct a 90% confidence interval from his results: 128,140,170,166,and 156.

How do the t and z distributions differ?

A sample of a given size is used to construct a 95% confidence interval for the population mean with a known population standard deviation.If a bigger sample had been used instead,then the 95% confidence interval would have been _ and the probability of making an error would have been __.

The minimum sample size n required to estimate a population mean with 95% confidence and the desired margin of error 1.5 was found to be 198.Which of the following is the approximate value of the assumed estimate of the population standard deviation?

We draw a random sample of size 25 from the normal population with the variance 2.4.If the sample mean is 12.5,what is a 99% confidence interval for the population mean?

What conditions are required by the central limit theorem before a confidence interval of the population mean may be created?

Construct a 90% confidence interval on the population proportion for the support of candidate A in the following mayoral election.Candidate A is facing two opposing candidates.In a recent poll of 300 residents,153 supported her.

The t distribution consists of a family of distributions where the actual shape of each one depends on the degrees of freedom,df.For lower values of df,the t distribution is similar to the z distribution.

The confidence intervals for the population proportion are generally based on ___________.

Statistics and Data

Tabular and Graphical Methods

Numerical Descriptive Measures

Basic Probability Concepts

Discrete Probability Distributions

Continuous Probability Distributions

Sampling and Sampling Distributions

Hypothesis Testing

Statistical Inference Concerning Two Populations

Statistical Inference Concerning Variance

Chi-Square Tests

Analysis of Variance

Regression Analysis

Inference With Regression Models

Regression Models for Nonlinear Relationships

Regression Models With Dummy Variables

Time Series and Forecasting

Returns, Index Numbers and Inflation

Nonparametric Tests

Filters

Exam 8: Interval Estimation

How is the efficiency of estimators defined?

The t distribution has broader tails than the z distribution.

Given a sample mean of 12.5-drawn from a normal population,a sample of size 25,and a sample variance of 2.4-find a 99% confidence interval for the population mean.

What is the minimum sample size required to estimate a population mean with 90% confidence when the desired margin of error is D = 1.25? The standard deviation in a preselected sample is 8.5.

A company manager thinks he is overpaying for fertilizer at $174 per ton.To find out,he collects fertilizer prices per ton from five distributors.Construct a 90% confidence interval from his results: 128,140,170,166,and 156.

How do the t and z distributions differ?

The minimum sample size n required to estimate a population mean with 95% confidence and the desired margin of error 1.5 was found to be 198.Which of the following is the approximate value of the assumed estimate of the population standard deviation?

We draw a random sample of size 25 from the normal population with the variance 2.4.If the sample mean is 12.5,what is a 99% confidence interval for the population mean?

What conditions are required by the central limit theorem before a confidence interval of the population mean may be created?

Construct a 90% confidence interval on the population proportion for the support of candidate A in the following mayoral election.Candidate A is facing two opposing candidates.In a recent poll of 300 residents,153 supported her.

The t distribution consists of a family of distributions where the actual shape of each one depends on the degrees of freedom,df.For lower values of df,the t distribution is similar to the z distribution.

The confidence intervals for the population proportion are generally based on ___________.

Statistics and Data

Tabular and Graphical Methods

Numerical Descriptive Measures

Basic Probability Concepts

Discrete Probability Distributions

Continuous Probability Distributions

Sampling and Sampling Distributions

Hypothesis Testing

Statistical Inference Concerning Two Populations

Statistical Inference Concerning Variance

Chi-Square Tests

Analysis of Variance

Regression Analysis

Inference With Regression Models

Regression Models for Nonlinear Relationships

Regression Models With Dummy Variables

Time Series and Forecasting

Returns, Index Numbers and Inflation

Nonparametric Tests

Filters