Question 1

In determining the sample size to estimate a population proportion,as p approaches .5,the calculated value of the sample size ______________.

Accepted Answer

A) Stays the same 
B) Decreases 
C) Increases 
A) Stays the same 
B) Decreases 
C) Increases C

Question 2

A botanist measures the heights of 16 seedlings and obtains a mean and standard deviation of 72.5 cm and 4.5 cm,respectively.Find the 95% confidence interval for the mean height of seedlings in the population form which the sample was selected.

Accepted Answer

A) [62.91 82.09] 
B) [70.30 74.70] 
C) [70.10 74.90] 
D) [70.54 74.46] 
E) [71.90 73.10] 
A) [62.91 82.09] 
B) [70.30 74.70] 
C) [70.10 74.90] 
D) [70.54 74.46] 
E) [71.90 73.10] C

Question 3

When the population is normally distributed,population standard deviation  $\sigma$ is unknown,and the sample size is n = 15;the confidence interval for the population mean µ is based on:

Accepted Answer

A) The z (normal)distribution 
B) The t distribution 
C) The Binomial distribution 
D) The Poisson distribution 
E) None of the above 
A) The z (normal)distribution 
B) The t distribution 
C) The Binomial distribution 
D) The Poisson distribution 
E) None of the above B

Question 4

What is a 95 percent confidence interval for µ when n = 10,   35.6,and s = 13.0? Assume population normality.

Accepted Answer

A) [26.44 44.76] 
B) [26.30 44.90] 
C) [33.02 38.18] 
D) [27.54 43.66] 
A) [26.44 44.76] 
B) [26.30 44.90] 
C) [33.02 38.18] 
D) [27.54 43.66]

Question 5

When the level of confidence and sample proportion   remain the same,a confidence interval for a population proportion p based on a sample of n = 100 will be ______________ a confidence interval for p based on a sample of n = 400.

Accepted Answer

A) Wider than 
B) Narrower than 
C) Equal to 
A) Wider than 
B) Narrower than 
C) Equal to

Question 6

When the population is normally distributed and the population standard deviation  $\sigma$ is unknown,then for any sample size n,the sampling distribution of   is based on the z distribution.

Accepted Answer

A) True 
 B)False

Question 7

The state highway department is studying traffic patterns on one of the busiest highways in the state.As part of the study,the department needs to estimate the average number of vehicles that pass an intersection each day.A random sample of 64 days gives us a sample mean of 14,205 cars and a sample standard deviation of 1,010 cars.What is the 92% confidence interval estimate of $\mu$,the mean number of cars passing the intersection?

Accepted Answer

A) [12,438 15,972] 
B) [14,028 14,382] 
C) [12,189 14,221] 
D) [13,984 14,426] 
E) [14,183 14,227] 
A) [12,438 15,972] 
B) [14,028 14,382] 
C) [12,189 14,221] 
D) [13,984 14,426] 
E) [14,183 14,227]

Question 8

As the sample size n increases,the width of the confidence interval _______________.

Accepted Answer

A) Stays the same 
B) Decreases 
C) Increases 
A) Stays the same 
B) Decreases 
C) Increases

Question 9

A manufacturer of dodge balls uses a machine to inflate its new balls to a pressure of 13.5 pounds (   = 0.1).When the machine is properly calibrated,the mean inflation pressure s 13.5 pounds,but uncontrollable factors can cause the pressure of individual dodge balls to vary.For quality control purposes,the manufacturer wishes to estimate the mean inflation pressure to within 0.025 pounds of its true value with a 99% confidence.What sample size should be used?

Accepted Answer

A) 677 
B) 107 
C) 35 
D) 27 
E) 11 
A) 677 
B) 107 
C) 35 
D) 27 
E) 11

Question 10

A confidence interval for the population mean is an interval constructed around the _____.

Accepted Answer

A) Sample mean 
B) Population mean 
C) Z test statistic 
D) t test statistic 
A) Sample mean 
B) Population mean 
C) Z test statistic 
D) t test statistic

Question 11

In a study of 265 subjects,the average score on the examination was 63.8 and s = 3.08.What is a 95 percent confidence for µ?

Accepted Answer

A) [63.59 64.01] 
B) [57.76 69.84] 
C) [63.43 64.17] 
D) [63.56 64.04] 
A) [63.59 64.01] 
B) [57.76 69.84] 
C) [63.43 64.17] 
D) [63.56 64.04]

Question 12

Health insurers and the federal government are both putting pressure on hospitals to shorten the average length of stay (LOS)of their patients.In 1996,the average LOS for non-heart patient was 4.6 days.A random sample of 20 hospitals in one state had a mean LOS for non-heart patients in 2000 of 3.8 days and a standard deviation of 1.2 days.How large a sample of hospitals would we need to be 99% confident that the sample mean is within 0.5 days of the population mean?

Accepted Answer

A) 3 
B) 7 
C) 32 
D) 48 
E) 96 
A) 3 
B) 7 
C) 32 
D) 48 
E) 96

Question 13

A sample of 100 items has a population standard deviation of 5.1 and a mean of 21.6.Construct a 95 percent confidence interval for   .

Accepted Answer

A) [11.60 31.60] 
B) [21.16 22.04] 
C) [20.60 22.60] 
D) [20.76 22.43] 
A) [11.60 31.60] 
B) [21.16 22.04] 
C) [20.60 22.60] 
D) [20.76 22.43]

Question 14

A random sample of size 15 is taken from a population assumed to be normal,and   = 1.2 and s = 0.6.Calculate a 90 percent confidence interval for   .

Accepted Answer

A) [.927 1.473] 
B) [.848 1.552] 
C) [.992 1.408] 
D) [1.045 1.355] 
A) [.927 1.473] 
B) [.848 1.552] 
C) [.992 1.408] 
D) [1.045 1.355]

Question 15

A company is interested in estimating   ,the mean number of days of sick leave taken by its employees.The firm's statistician randomly selects 100 personnel files and notes the number of sick days taken by each employee.The sample mean is 12.2 days and the sample standard deviation is 10 days.How many personnel files would the director have to select in order to estimate $\mu$ to within 2 days with a 99% confidence interval?

Accepted Answer

A) 2 
B) 13 
C) 136 
D) 165 
E) 166 
A) 2 
B) 13 
C) 136 
D) 165 
E) 166

Question 16

As the stated confidence level decreases,the width of the confidence interval _______________.

Accepted Answer

A) Stays the same 
B) Decreases 
C) Increases 
A) Stays the same 
B) Decreases 
C) Increases

Question 17

When the margin of error is added to and subtracted from the sample mean an interval is formed that will contain $\mu$ with probability of (1 - $\alpha$).

Accepted Answer

A) True 
 B)False

Question 18

When the sample size and sample standard deviation remain the same,a 99% confidence interval for a population mean,µ will be narrower than the 95% confidence interval for µ.

Accepted Answer

A) True 
 B)False

Question 19

In a random sample of 651 computer scientists who subscribed to a web-based daily news update,it was found that the average salary was $46,816 with a standard deviation of $12,557.Calculate a 91% confidence interval for the mean salary of computer scientists.

Accepted Answer

A) [$25,469 $68,163] 
B) [$46,592 $47,040] 
C) [$46,157 $47,475] 
D) [$46,783 $46,849] 
E) [$45,979 $47,653] 
A) [$25,469 $68,163] 
B) [$46,592 $47,040] 
C) [$46,157 $47,475] 
D) [$46,783 $46,849] 
E) [$45,979 $47,653]

Question 20

If the 95% confidence interval for a mean is from .771 to 1.629,can we conclude that   = .5,using a 95 percent confidence interval?

Accepted Answer

A) Yes 
B) No 
A) Yes 
B) No

In determining the sample size to estimate a population proportion,as p approaches .5,the calculated value of the sample size ______________.

A botanist measures the heights of 16 seedlings and obtains a mean and standard deviation of 72.5 cm and 4.5 cm,respectively.Find the 95% confidence interval for the mean height of seedlings in the population form which the sample was selected.

When the population is normally distributed,population standard deviation $\sigma$ is unknown,and the sample size is n = 15;the confidence interval for the population mean µ is based on:

What is a 95 percent confidence interval for µ when n = 10, 35.6,and s = 13.0? Assume population normality.

When the level of confidence and sample proportion remain the same,a confidence interval for a population proportion p based on a sample of n = 100 will be ______________ a confidence interval for p based on a sample of n = 400.

As the sample size n increases,the width of the confidence interval _______________.

A confidence interval for the population mean is an interval constructed around the _____.

In a study of 265 subjects,the average score on the examination was 63.8 and s = 3.08.What is a 95 percent confidence for µ?

A sample of 100 items has a population standard deviation of 5.1 and a mean of 21.6.Construct a 95 percent confidence interval for .

A random sample of size 15 is taken from a population assumed to be normal,and = 1.2 and s = 0.6.Calculate a 90 percent confidence interval for .

As the stated confidence level decreases,the width of the confidence interval _______________.

When the margin of error is added to and subtracted from the sample mean an interval is formed that will contain $\mu$ with probability of (1 - $\alpha$ ).

When the sample size and sample standard deviation remain the same,a 99% confidence interval for a population mean,µ will be narrower than the 95% confidence interval for µ.

In a random sample of 651 computer scientists who subscribed to a web-based daily news update,it was found that the average salary was $46,816 with a standard deviation of $12,557.Calculate a 91% confidence interval for the mean salary of computer scientists.

If the 95% confidence interval for a mean is from .771 to 1.629,can we conclude that = .5,using a 95 percent confidence interval?

An Introduction to Business Statistics

Descriptive Statistics: Tabular and Graphical Methods

Descriptive Statistics: Numerical Methods

Probability

Discrete Random Variables

Continuous Random Variables

Sampling and Sampling Distributions

Hypothesis Testing

Statistical Inferences Based on Two Samples

Experimental Design and Analysis of Variance

Chi-Square Tests

Simple Linear Regression Analysis

Multiple Regression

Model Building and Model Diagnostics

Time Series Forecasting

Process Improvement Using Control Charts

Nonparametric Methods

Decision Theory

Filters

Exam 8: Confidence Intervals

In determining the sample size to estimate a population proportion,as p approaches .5,the calculated value of the sample size ______________.

A botanist measures the heights of 16 seedlings and obtains a mean and standard deviation of 72.5 cm and 4.5 cm,respectively.Find the 95% confidence interval for the mean height of seedlings in the population form which the sample was selected.

When the population is normally distributed,population standard deviation σ\sigmaσ is unknown,and the sample size is n = 15;the confidence interval for the population mean µ is based on:

What is a 95 percent confidence interval for µ when n = 10, 35.6,and s = 13.0? Assume population normality.

When the level of confidence and sample proportion remain the same,a confidence interval for a population proportion p based on a sample of n = 100 will be ______________ a confidence interval for p based on a sample of n = 400.

When the population is normally distributed and the population standard deviation σ\sigmaσ is unknown,then for any sample size n,the sampling distribution of is based on the z distribution.

As the sample size n increases,the width of the confidence interval _______________.

A confidence interval for the population mean is an interval constructed around the _____.

In a study of 265 subjects,the average score on the examination was 63.8 and s = 3.08.What is a 95 percent confidence for µ?

A sample of 100 items has a population standard deviation of 5.1 and a mean of 21.6.Construct a 95 percent confidence interval for .

A random sample of size 15 is taken from a population assumed to be normal,and = 1.2 and s = 0.6.Calculate a 90 percent confidence interval for .

As the stated confidence level decreases,the width of the confidence interval _______________.

When the margin of error is added to and subtracted from the sample mean an interval is formed that will contain μ\muμ with probability of (1 - α\alphaα ).

When the sample size and sample standard deviation remain the same,a 99% confidence interval for a population mean,µ will be narrower than the 95% confidence interval for µ.

In a random sample of 651 computer scientists who subscribed to a web-based daily news update,it was found that the average salary was $46,816 with a standard deviation of $12,557.Calculate a 91% confidence interval for the mean salary of computer scientists.

If the 95% confidence interval for a mean is from .771 to 1.629,can we conclude that = .5,using a 95 percent confidence interval?

An Introduction to Business Statistics

Descriptive Statistics: Tabular and Graphical Methods

Descriptive Statistics: Numerical Methods

Probability

Discrete Random Variables

Continuous Random Variables

Sampling and Sampling Distributions

Hypothesis Testing

Statistical Inferences Based on Two Samples

Experimental Design and Analysis of Variance

Chi-Square Tests

Simple Linear Regression Analysis

Multiple Regression

Model Building and Model Diagnostics

Time Series Forecasting

Process Improvement Using Control Charts

Nonparametric Methods

Decision Theory

Filters

When the population is normally distributed,population standard deviation $\sigma$ is unknown,and the sample size is n = 15;the confidence interval for the population mean µ is based on:

When the margin of error is added to and subtracted from the sample mean an interval is formed that will contain $\mu$ with probability of (1 - $\alpha$ ).