Question 1

The tdf distribution has broader tails than the z distribution.

Accepted Answer

A) True 
 B)False

Question 2

A machine that is programmed to package 1.20 pounds of cereal is being tested for its accuracy in a sample of 36 cereal boxes, the sample mean filling weight is calculated as 1.22 pounds. The population standard deviation is known to be 0.06 pounds. Find the 95% confidence interval for the mean.

Accepted Answer

A)  [1.20, 1.24] 
B)  [1.18, 1.26] 
C)  [1.16, 1.28] 
D)  [1.14, 1.30] 
A)  [1.20, 1.24] 
B)  [1.18, 1.26] 
C)  [1.16, 1.28] 
D)  [1.14, 1.30]

Question 3

The width of the confidence interval is ________ times the margin of error.

Accepted Answer

The answer of The width of the confidence interval is...

Question 4

The tdf 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 tdf distribution is similar to the z distribution.

Accepted Answer

A) True 
 B)False

Question 5

To construct a 95% confidence interval for µ, the sampling distribution of   must be ________.

Accepted Answer

The answer of To construct a 95% confidence interval for...

Question 6

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

[135.1059,

Question 7

At a particular academically challenging high school, the average GPA of a high school senior is known to be normally distributed. After a sample of 20 seniors is taken, the average GPA is found to be 2.71 and the variance is determined to be 0.25. Find a 90% confidence interval for the population mean GPA.

Accepted Answer

A)  [2.5167, 2.9033] 
B)  [2.5261, 2.8961] 
C)  [2.5615, 2.8585] 
D)  [2.6358, 2.7842] 
A)  [2.5167, 2.9033] 
B)  [2.5261, 2.8961] 
C)  [2.5615, 2.8585] 
D)  [2.6358, 2.7842]

Question 8

When examining the possible outcome of an election, what type of confidence interval is most suitable for estimating the current support for a candidate?

Accepted Answer

A)  The confidence interval for the sample mean 
B)  The confidence interval for the population mean 
C)  The confidence interval for the sample proportion 
D)  The confidence interval for the population proportion 
A)  The confidence interval for the sample mean 
B)  The confidence interval for the population mean 
C)  The confidence interval for the sample proportion 
D)  The confidence interval for the population proportion

Question 9

According to a report in USA Today, more and more parents are helping their young adult children get homes. Suppose eight persons in a random sample of 40 young adults who recently purchased a home in Kentucky received 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 received help from their parents. If a 99% confidence interval is constructed instead of a 95% confidence interval for the population proportion, then ________.

Accepted Answer

A)  the resulting margin of error will increase and the risk of reporting an incorrect interval will increase 
B)  the resulting margin of error will decrease and the risk of reporting an incorrect interval will increase 
C)  the resulting margin of error will increase and the risk of reporting an incorrect interval will decrease 
D)  the resulting margin of error will decrease and the risk of reporting an incorrect interval will decrease 
A)  the resulting margin of error will increase and the risk of reporting an incorrect interval will increase 
B)  the resulting margin of error will decrease and the risk of reporting an incorrect interval will increase 
C)  the resulting margin of error will increase and the risk of reporting an incorrect interval will decrease 
D)  the resulting margin of error will decrease and the risk of reporting an incorrect interval will decrease

Question 10

The minimum sample size n required to estimate a population mean with 95% confidence and the assumed estimate of the population standard deviation 6.5 was found to be 124. Which of the following is the approximate value of the assumed desired margin of error?

Accepted Answer

A)  D = 0.9220 
B)  D = 0.9602 
C)  D = 1.1441 
D)  D = 1.3090 
A)  D = 0.9220 
B)  D = 0.9602 
C)  D = 1.1441 
D)  D = 1.3090

Question 11

A large university is interested in the outcome of a course standardization process. They have learned that 150 students of the total 1,500 students failed to pass the course in the current semester. Construct a 99% confidence interval on the population proportion of students who failed to pass the course. Was the normality condition met for the validity of the confidence interval formula?

Accepted Answer

[0.0800, 0

Question 12

A budget airline wants to estimate what proportion of customers would pay $10 for in-flight wireless access. Given that the airline has no prior knowledge of the proportion, how many customers would it have to sample to ensure a margin of error of no more than 5% for a 95% confidence interval?

Accepted Answer

The answer of A budget airline wants to estimate what...

Question 13

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....

Question 14

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 15

The ________ determine the extent of the broadness of the tails of the distribution.

Accepted Answer

The answer of The ________ determine the extent of the...

Question 16

A sample of 1,400 American households was asked if they planned to buy a new car next year. Of the respondents, 34% indicated they planned to buy a new car next year. Construct a 90% confidence interval of the proportion of American households who expect to buy a new car next year.

Accepted Answer

A)  [0.3152, 0.3648] 
B)  [0.3192, 0.3608] 
C)  [0.3394, 0.3406] 
D)  [0.3354, 0.3446] 
A)  [0.3152, 0.3648] 
B)  [0.3192, 0.3608] 
C)  [0.3394, 0.3406] 
D)  [0.3354, 0.3446]

Question 17

Suppose we wish to find the required sample size to find a 90% confidence interval for the population proportion with the desired margin of error. If there is no rough estimate   of the population proportion, what value should be assumed for   ?

Accepted Answer

A)  0.05 
B)  0.10 
C)  0.50 
D)  0.90 
A)  0.05 
B)  0.10 
C)  0.50 
D)  0.90

Question 18

Given a sample mean of 27 and a sample standard deviation of 3.5 computed from a sample of size 36, find a 95% confidence interval on the population mean.

Accepted Answer

A)  [25.8158, 28.1842] 
B)  [25.8170, 28.1830] 
C)  [26.0142, 27.9858] 
D)  [26.9930, 27.0070] 
A)  [25.8158, 28.1842] 
B)  [25.8170, 28.1830] 
C)  [26.0142, 27.9858] 
D)  [26.9930, 27.0070]

Question 19

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 with a standard deviation of $16 thousand. Assume the distribution is normally distributed. Construct a 95% confidence interval for the salary of new accounting professors. Answers are in thousands of dollars.

Accepted Answer

A)  [102.1680, 167.832] 
B)  [127.8247, 142.1753] 
C)  [128.7958, 141.2042] 
D)  [129.0735, 140.9265] 
A)  [102.1680, 167.832] 
B)  [127.8247, 142.1753] 
C)  [128.7958, 141.2042] 
D)  [129.0735, 140.9265]

Question 20

For a given sample size and population standard deviation, which of the following is true in the interval estimation of the population mean?

Accepted Answer

A)  If the confidence level is greater, the interval is wider. 
B)  If the confidence level is smaller, the interval is wider. 
C)  If the confidence level is greater, the interval is narrower. 
D)  None of the above 
A)  If the confidence level is greater, the interval is wider. 
B)  If the confidence level is smaller, the interval is wider. 
C)  If the confidence level is greater, the interval is narrower. 
D)  None of the above

The t_df distribution has broader tails than the z distribution.

A machine that is programmed to package 1.20 pounds of cereal is being tested for its accuracy in a sample of 36 cereal boxes, the sample mean filling weight is calculated as 1.22 pounds. The population standard deviation is known to be 0.06 pounds. Find the 95% confidence interval for the mean.

The width of the confidence interval is ________ times the margin of error.

The t_dfdistribution 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_df distribution is similar to the z distribution.

To construct a 95% confidence interval for µ, the sampling distribution of must be ________.

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.

When examining the possible outcome of an election, what type of confidence interval is most suitable for estimating the current support for a candidate?

The minimum sample size n required to estimate a population mean with 95% confidence and the assumed estimate of the population standard deviation 6.5 was found to be 124. Which of the following is the approximate value of the assumed desired margin of error?

A budget airline wants to estimate what proportion of customers would pay $10 for in-flight wireless access. Given that the airline has no prior knowledge of the proportion, how many customers would it have to sample to ensure a margin of error of no more than 5% for a 95% confidence interval?

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.

The ________ determine the extent of the broadness of the tails of the distribution.

A sample of 1,400 American households was asked if they planned to buy a new car next year. Of the respondents, 34% indicated they planned to buy a new car next year. Construct a 90% confidence interval of the proportion of American households who expect to buy a new car next year.

Suppose we wish to find the required sample size to find a 90% confidence interval for the population proportion with the desired margin of error. If there is no rough estimate of the population proportion, what value should be assumed for ?

Given a sample mean of 27 and a sample standard deviation of 3.5 computed from a sample of size 36, find a 95% confidence interval on the population mean.

For a given sample size and population standard deviation, which of the following is true in the interval estimation of the population mean?

Statistics and Data

Tabular and Graphical Methods

Numerical Descriptive Measures

Introduction to Probability

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

The tdf distribution has broader tails than the z distribution.

A machine that is programmed to package 1.20 pounds of cereal is being tested for its accuracy in a sample of 36 cereal boxes, the sample mean filling weight is calculated as 1.22 pounds. The population standard deviation is known to be 0.06 pounds. Find the 95% confidence interval for the mean.

The width of the confidence interval is ________ times the margin of error.

The tdf 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 tdf distribution is similar to the z distribution.

To construct a 95% confidence interval for µ, the sampling distribution of must be ________.

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.

When examining the possible outcome of an election, what type of confidence interval is most suitable for estimating the current support for a candidate?

The minimum sample size n required to estimate a population mean with 95% confidence and the assumed estimate of the population standard deviation 6.5 was found to be 124. Which of the following is the approximate value of the assumed desired margin of error?

A budget airline wants to estimate what proportion of customers would pay $10 for in-flight wireless access. Given that the airline has no prior knowledge of the proportion, how many customers would it have to sample to ensure a margin of error of no more than 5% for a 95% confidence interval?

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.

The ________ determine the extent of the broadness of the tails of the distribution.

A sample of 1,400 American households was asked if they planned to buy a new car next year. Of the respondents, 34% indicated they planned to buy a new car next year. Construct a 90% confidence interval of the proportion of American households who expect to buy a new car next year.

Suppose we wish to find the required sample size to find a 90% confidence interval for the population proportion with the desired margin of error. If there is no rough estimate of the population proportion, what value should be assumed for ?

Given a sample mean of 27 and a sample standard deviation of 3.5 computed from a sample of size 36, find a 95% confidence interval on the population mean.

For a given sample size and population standard deviation, which of the following is true in the interval estimation of the population mean?

Statistics and Data

Tabular and Graphical Methods

Numerical Descriptive Measures

Introduction to Probability

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

The t_df distribution has broader tails than the z distribution.

The t_dfdistribution 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_df distribution is similar to the z distribution.