Question 1

The z value for a 97.8% confidence interval estimation is

Accepted Answer

A)  2.02. 
B)  1.96. 
C)  2.00. 
D)  2.29. 
A)  2.02. 
B)  1.96. 
C)  2.00. 
D)  2.29.

Question 2

In an interval estimation for a proportion of a population, the value of z at 99.2% confidence is

Accepted Answer

A)  2.65. 
B)  2.41. 
C)  1.96. 
D)  1.645. 
A)  2.65. 
B)  2.41. 
C)  1.96. 
D)  1.645.

Question 3

In order to estimate the average time spent per student on the computer terminals at a local university, data were collected for a sample of 81 business students over a one-week period.Assume the population standard deviation is 1.8 hours.If the sample mean is 9 hours, then the 95% confidence interval is

Accepted Answer

A)  ​7.04 to 10.96 hours. 
B)  ​7.36 to 10.64 hours. 
C)  ​7.80 to 10.20 hours. 
D)  ​8.61 to 9.39 hours. 
A)  ​7.04 to 10.96 hours. 
B)  ​7.36 to 10.64 hours. 
C)  ​7.80 to 10.20 hours. 
D)  ​8.61 to 9.39 hours.

Question 4

A sample of 75 information systems managers had an average hourly income of $40.75 with a standard deviation of $7.00.The 95% confidence interval for the average hourly wage (in $) of all information system managers is

Accepted Answer

A)  38.61 to 42.89. 
B)  39.40 to 42.10. 
C)  39.14 to 42.36. 
D)  37.54 to 43.96. 
A)  38.61 to 42.89. 
B)  39.40 to 42.10. 
C)  39.14 to 42.36. 
D)  37.54 to 43.96.

Question 5

A machine that produces a major part for an airplane engine is monitored closely.In the past, 10% of the parts produced would be defective.With a .95 probability, the sample size that needs to be taken if the desired margin of error is .04 or less is

Accepted Answer

A)  110. 
B)  111. 
C)  216. 
D)  217. 
A)  110. 
B)  111. 
C)  216. 
D)  217.

Question 6

We are interested in conducting a study in order to determine the percentage of voters in a city who would vote for the incumbent mayor.What is the minimum sample size needed to estimate the population proportion with a margin of error not exceeding 4% at 95% confidence?

Accepted Answer

A)  625 
B)  626 
C)  600 
D)  601 
A)  625 
B)  626 
C)  600 
D)  601

Question 7

A 95% confidence interval for a population mean is determined to be 100 to 120.For the same data, if the confidence coefficient is reduced to .90, the confidence interval for μ

Accepted Answer

A)  becomes narrower. 
B)  becomes wider. 
C)  does not change. 
D)  becomes 100.1 to 120.1. 
A)  becomes narrower. 
B)  becomes wider. 
C)  does not change. 
D)  becomes 100.1 to 120.1.

Question 8

As the sample size increases, the margin of error

Accepted Answer

A)  increases. 
B)  decreases. 
C)  stays the same. 
D)  fluctuates depending on the mean. 
A)  increases. 
B)  decreases. 
C)  stays the same. 
D)  fluctuates depending on the mean.

Question 9

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

Accepted Answer

A)  ​population mean, standard error 
B)  population proportion, standard error 
C)  ​point estimate, margin of error 
D)  ​planning value, confidence coefficient 
A)  ​population mean, standard error 
B)  population proportion, standard error 
C)  ​point estimate, margin of error 
D)  ​planning value, confidence coefficient

Question 10

The manager of a grocery store has taken a random sample of 100 customers.The average length of time it took these 100 customers to check out was 3 minutes.It is known that the standard deviation of the population of checkout times is 1 minute.With a .95 probability, the sample mean will provide a margin of error of

Accepted Answer

A)  1.96. 
B)  .10. 
C)  .196. 
D)  1.64. 
A)  1.96. 
B)  .10. 
C)  .196. 
D)  1.64.

Question 11

A random sample of 1000 people was taken.Four hundred fifty of the people in the sample favored Candidate A.The 95% confidence interval for the true proportion of people who favor Candidate A is

Accepted Answer

A)  .419 to .481. 
B)  .40 to .50. 
C)  .45 to .55. 
D)  .424 to .476. 
A)  .419 to .481. 
B)  .40 to .50. 
C)  .45 to .55. 
D)  .424 to .476.

Question 12

In order to estimate the average electric usage per month, a sample of 81 houses was selected and the electric usage was determined.Assume a population standard deviation of 450 kilowatt-hours.If the sample mean is 1858 kWh, the 95% confidence interval estimate of the population mean is

Accepted Answer

A)  1760 to 1956 kWh. 
B)  1729 to 1987 kWh. 
C)  1758 to 1958 kWh. 
D)  1776 to 1940 kWh. 
A)  1760 to 1956 kWh. 
B)  1729 to 1987 kWh. 
C)  1758 to 1958 kWh. 
D)  1776 to 1940 kWh.

Question 13

In general, higher confidence levels provide

Accepted Answer

A)  wider confidence intervals. 
B)  narrower confidence intervals. 
C)  a smaller standard error. 
D)  unbiased estimates. 
A)  wider confidence intervals. 
B)  narrower confidence intervals. 
C)  a smaller standard error. 
D)  unbiased estimates.

Question 14

A random sample of 64 SAT scores of students applying for merit scholarships showed an average of 1400 with a standard deviation of 240.If we want to provide a 95% confidence interval for the population mean SAT score, the degrees of freedom for reading the t value is

Accepted Answer

A)  60. 
B)  61. 
C)  62. 
D)  63. 
A)  60. 
B)  61. 
C)  62. 
D)  63.

Question 15

A random sample of 64 SAT scores of students applying for merit scholarships showed an average of 1400 with a standard deviation of 240.The t value needed to develop the 95% confidence interval for the population mean SAT score is

Accepted Answer

A)  1.96. 
B)  1.998. 
C)  1.645. 
D)  1.28. 
A)  1.96. 
B)  1.998. 
C)  1.645. 
D)  1.28.

Question 16

A sample of 225 elements from a population with a standard deviation of 75 is selected.The sample mean is 180.The 95% confidence interval for μ is

Accepted Answer

A)  105 to 225. 
B)  175 to 185. 
C)  171.78 to 188.22. 
D)  170.2 to 189.8. 
A)  105 to 225. 
B)  175 to 185. 
C)  171.78 to 188.22. 
D)  170.2 to 189.8.

Question 17

A sample of 200 elements from a population with a known standard deviation is selected.For an interval estimation of μ, the proper distribution to use is the

Accepted Answer

A)  normal distribution. 
B)  t distribution with 200 degrees of freedom. 
C)  t distribution with 201 degrees of freedom. 
D)  t distribution with 199 degrees of freedom. 
A)  normal distribution. 
B)  t distribution with 200 degrees of freedom. 
C)  t distribution with 201 degrees of freedom. 
D)  t distribution with 199 degrees of freedom.

Question 18

To compute the minimum sample size for an interval estimate  , we must first determine all of the following except?

Accepted Answer

A)   desired margin of error. 
B)   confidence level. 
C)   population standard deviation. 
D)   degrees of freedom. 
A)   desired margin of error. 
B)   confidence level. 
C)   population standard deviation. 
D)   degrees of freedom.

Question 19

The level of significance α

Accepted Answer

A)  can be any positive value. 
B)  is always a negative value. 
C)  is (1 - confidence coefficient). 
D)  can be any value between -1.96 to 1.96. 
A)  can be any positive value. 
B)  is always a negative value. 
C)  is (1 - confidence coefficient). 
D)  can be any value between -1.96 to 1.96.

Question 20

The manager of a grocery store has taken a random sample of 100 customers.The average length of time it took these 100 customers to check out was 3 minutes.It is known that the standard deviation of the population of checkout times is 1 minute.The 95% confidence interval for the true average checkout time (in minutes) is

Accepted Answer

A)  2.5 to 3.5. 
B)  1.36 to 4.64. 
C)  1 to 5. 
D)  2.804 to 3.196. 
A)  2.5 to 3.5. 
B)  1.36 to 4.64. 
C)  1 to 5. 
D)  2.804 to 3.196.

The z value for a 97.8% confidence interval estimation is

In an interval estimation for a proportion of a population, the value of z at 99.2% confidence is

A sample of 75 information systems managers had an average hourly income of $40.75 with a standard deviation of $7.00.The 95% confidence interval for the average hourly wage (in $) of all information system managers is

A machine that produces a major part for an airplane engine is monitored closely.In the past, 10% of the parts produced would be defective.With a .95 probability, the sample size that needs to be taken if the desired margin of error is .04 or less is

We are interested in conducting a study in order to determine the percentage of voters in a city who would vote for the incumbent mayor.What is the minimum sample size needed to estimate the population proportion with a margin of error not exceeding 4% at 95% confidence?

A 95% confidence interval for a population mean is determined to be 100 to 120.For the same data, if the confidence coefficient is reduced to .90, the confidence interval for μ

As the sample size increases, the margin of error

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

A random sample of 1000 people was taken.Four hundred fifty of the people in the sample favored Candidate A.The 95% confidence interval for the true proportion of people who favor Candidate A is

In order to estimate the average electric usage per month, a sample of 81 houses was selected and the electric usage was determined.Assume a population standard deviation of 450 kilowatt-hours.If the sample mean is 1858 kWh, the 95% confidence interval estimate of the population mean is

In general, higher confidence levels provide

A random sample of 64 SAT scores of students applying for merit scholarships showed an average of 1400 with a standard deviation of 240.If we want to provide a 95% confidence interval for the population mean SAT score, the degrees of freedom for reading the t value is

A random sample of 64 SAT scores of students applying for merit scholarships showed an average of 1400 with a standard deviation of 240.The t value needed to develop the 95% confidence interval for the population mean SAT score is

A sample of 225 elements from a population with a standard deviation of 75 is selected.The sample mean is 180.The 95% confidence interval for μ is

A sample of 200 elements from a population with a known standard deviation is selected.For an interval estimation of μ, the proper distribution to use is the

To compute the minimum sample size for an interval estimate of, we must first determine all of the following except?

The level of significance α

Data and Statistics

Descriptive Statistics: Tabulargraphical

Descriptive Statistics: Numerical

Introduction to Probability

Discrete Probability Distributions

Continuous Probability Distributions

Sampling and Sampling Distributions

Hypothesis Tests

Inference About Means and Proportions With Two Populations

Inferences About Population Variances

Comparing Multiple Proportions, Test of Independence and Goodness of Fit

Experimental Design and Analysis of Variance

Simple Linear Regression

Multiple Regression

Filters

Exam 8: Interval Estimation

The z value for a 97.8% confidence interval estimation is

In an interval estimation for a proportion of a population, the value of z at 99.2% confidence is

A sample of 75 information systems managers had an average hourly income of $40.75 with a standard deviation of $7.00.The 95% confidence interval for the average hourly wage (in $) of all information system managers is

A machine that produces a major part for an airplane engine is monitored closely.In the past, 10% of the parts produced would be defective.With a .95 probability, the sample size that needs to be taken if the desired margin of error is .04 or less is

We are interested in conducting a study in order to determine the percentage of voters in a city who would vote for the incumbent mayor.What is the minimum sample size needed to estimate the population proportion with a margin of error not exceeding 4% at 95% confidence?

A 95% confidence interval for a population mean is determined to be 100 to 120.For the same data, if the confidence coefficient is reduced to .90, the confidence interval for μ

As the sample size increases, the margin of error

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

A random sample of 1000 people was taken.Four hundred fifty of the people in the sample favored Candidate A.The 95% confidence interval for the true proportion of people who favor Candidate A is

In order to estimate the average electric usage per month, a sample of 81 houses was selected and the electric usage was determined.Assume a population standard deviation of 450 kilowatt-hours.If the sample mean is 1858 kWh, the 95% confidence interval estimate of the population mean is

In general, higher confidence levels provide

A random sample of 64 SAT scores of students applying for merit scholarships showed an average of 1400 with a standard deviation of 240.If we want to provide a 95% confidence interval for the population mean SAT score, the degrees of freedom for reading the t value is

A random sample of 64 SAT scores of students applying for merit scholarships showed an average of 1400 with a standard deviation of 240.The t value needed to develop the 95% confidence interval for the population mean SAT score is

A sample of 225 elements from a population with a standard deviation of 75 is selected.The sample mean is 180.The 95% confidence interval for μ is

A sample of 200 elements from a population with a known standard deviation is selected.For an interval estimation of μ, the proper distribution to use is the

To compute the minimum sample size for an interval estimate of, we must first determine all of the following except?

The level of significance α

Data and Statistics

Descriptive Statistics: Tabulargraphical

Descriptive Statistics: Numerical

Introduction to Probability

Discrete Probability Distributions

Continuous Probability Distributions

Sampling and Sampling Distributions

Hypothesis Tests

Inference About Means and Proportions With Two Populations

Inferences About Population Variances

Comparing Multiple Proportions, Test of Independence and Goodness of Fit

Experimental Design and Analysis of Variance

Simple Linear Regression

Multiple Regression

Filters

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