Question 1

The tolerance interval of 95.44 percent is ________ a 95.44 percent confidence interval.

Accepted Answer

A)  the same width as 
B)  narrower than 
C)  wider than 
A)  the same width as 
B)  narrower than 
C)  wider than

Question 2

The exact spread of the t distribution depends on the ________.

Accepted Answer

A)  standard deviation of the sample 
B)  sample size n 
C)  number of degrees of freedom 
D)  z distribution 
A)  standard deviation of the sample 
B)  sample size n 
C)  number of degrees of freedom 
D)  z distribution

Question 3

Which of the following is an advantage of a confidence interval estimate over a point estimate for a population parameter?

Accepted Answer

A)  Interval estimates are more precise than point estimates. 
B)  Interval estimates are less accurate than point estimates. 
C)  Interval estimates are both more accurate and more precise than point estimates. 
D)  Interval estimates take into account the fact that the statistic that is used to estimate the population parameter is a random variable. 
A)  Interval estimates are more precise than point estimates. 
B)  Interval estimates are less accurate than point estimates. 
C)  Interval estimates are both more accurate and more precise than point estimates. 
D)  Interval estimates take into account the fact that the statistic that is used to estimate the population parameter is a random variable.

Question 4

An environmental group at a local college is conducting independent tests to determine the distance a particular make of automobile will travel while consuming only 1 gallon of gas. They test a sample of five cars and obtain a mean of 28.2 miles. Assuming that the population standard deviation is 2.7 miles, find the 95 percent confidence interval for the mean distance traveled by all such cars using 1 gallon of gas.

Accepted Answer

A)  [26.16, 30.24] 
B)  [20.70, 35.70] 
C)  [24.85, 31.55] 
D)  [26.70, 29.70] 
E)  [25.83, 30.57] 
A)  [26.16, 30.24] 
B)  [20.70, 35.70] 
C)  [24.85, 31.55] 
D)  [26.70, 29.70] 
E)  [25.83, 30.57]

Question 5

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

Question 6

Researchers studied the role that the age of workers has in determining the hours per month spent on personal tasks. A sample of 1,686 adults were observed for one month. The data follow.   Construct an 88 percent confidence interval for the mean hours spent on personal tasks for 18- to 24-year-olds.

Accepted Answer

A)  [4.09, 4.25] 
B)  [4.11, 4.23] 
C)  [4.08, 4.26] 
D)  [4.14, 4.20] 
E)  [4.15, 4.19] 
A)  [4.09, 4.25] 
B)  [4.11, 4.23] 
C)  [4.08, 4.26] 
D)  [4.14, 4.20] 
E)  [4.15, 4.19]

Question 7

A confidence interval increases in width as

Accepted Answer

A)  the level of confidence increases. 
B)  n decreases. 
C)  s increases. 
D)  All of these answers are correct. 
A)  the level of confidence increases. 
B)  n decreases. 
C)  s increases. 
D)  All of these answers are correct.

Question 8

A local country club golf tournament organizer is attempting to estimate the average number of strokes for the 13th hole. On a particular day, 64 players completed the play on the 13th hole, with an average of 4.25 strokes and a population standard deviation of 1.6 strokes. Determine the 95 percent confidence interval for the average number of strokes.

Accepted Answer

A)  [3.94, 4.56] 
B)  [3.86, 4.64] 
C)  [4.05, 4.45] 
D)  [3.92, 4.58] 
A)  [3.94, 4.56] 
B)  [3.86, 4.64] 
C)  [4.05, 4.45] 
D)  [3.92, 4.58]

Question 9

What sample size is needed to estimate with 95 percent confidence the mean intake of daily calcium within 20 units of the true mean if the intake is normally distributed with a variance of 1900 units?

Accepted Answer

A)  34,671 
B)  187 
C)  32 
D)  19 
A)  34,671 
B)  187 
C)  32 
D)  19

Question 10

When sample size is 16, find t.025.

Accepted Answer

2.131
df =

Question 11

When the level of confidence and sample size remain the same, a confidence interval for a population proportion, p, will be narrower when   (1 −   ) is larger than when   (1 −   )] is smaller.

Accepted Answer

A) True 
 B)False

Question 12

In a randomly selected group of 650 automobile deaths, 180 were alcohol related. Construct a 95 percent confidence interval for the true proportion of all automobile accidents caused by alcohol.

Accepted Answer

A)  [.243, .311] 
B)  [.262, .292] 
C)  [.259, .294] 
D)  [.263, .291] 
A)  [.243, .311] 
B)  [.262, .292] 
C)  [.259, .294] 
D)  [.263, .291]

Question 13

In a manufacturing process, a random sample of 36 manufactured bolts has a mean length of 3 inches with a standard deviation of .3 inches. What is the 99 percent confidence interval for the true mean length of the manufactured bolt?

Accepted Answer

A)  2.902 to 3.098 
B)  2.884 to 3.117 
C)  2.864 to 3.136 
D)  2.228 to 3.772 
E)  2.802 to 3.198 
A)  2.902 to 3.098 
B)  2.884 to 3.117 
C)  2.864 to 3.136 
D)  2.228 to 3.772 
E)  2.802 to 3.198

Question 14

In a study of factors affecting whether soldiers decide to reenlist, 320 subjects were measured for an index of satisfaction. The sample mean is 28.8 and the sample standard deviation is 7.3. Use the given sample data to construct the 98 percent confidence interval for the population mean for level of satisfaction.

Accepted Answer

A)  [27.85, 29.75] 
B)  [27.96, 29.64] 
C)  [11.82, 45.78] 
D)  [28.75, 28.85] 
E)  [28.60, 29.00] 
A)  [27.85, 29.75] 
B)  [27.96, 29.64] 
C)  [11.82, 45.78] 
D)  [28.75, 28.85] 
E)  [28.60, 29.00]

Question 15

In a survey of 1,000 people, 420 are opposed to an income tax increase. Construct a 95 percent confidence interval for the proportion of people in the population opposed to this tax increase.

Accepted Answer

A)  [.394, .446] 
B)  [.389, .451] 
C)  [.380, .460] 
D)  [.399, .441] 
A)  [.394, .446] 
B)  [.389, .451] 
C)  [.380, .460] 
D)  [.399, .441]

Question 16

A sample of 12 items yields   = 48.5 grams and s = 1.5 grams. Assuming a normal distribution, construct a 90 percent confidence interval for the population mean weight.

Accepted Answer

A)  [47.722, 49.278] 
B)  [47.788, 49.212] 
C)  [45.806, 51.194] 
D)  [47.865, 49.135] 
A)  [47.722, 49.278] 
B)  [47.788, 49.212] 
C)  [45.806, 51.194] 
D)  [47.865, 49.135]

Question 17

In a manufacturing process, we are interested in measuring the average length of a certain type of bolt. Based on a preliminary sample of 9 manufactured bolts, the sample standard deviation is .3 inches. How many bolts should be sampled in order to make us 95 percent confident that the sample mean bolt length is within .02 inches of the true mean bolt length?

Accepted Answer

1197 n = ([(t_α_/2 × s)/E

Question 18

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. After calculating the confidence interval, the highway department officials decide that the precision is too low for their needs. They feel the precision should be 300 cars. Given this precision, and needing to be 99 percent confident, how many days do they need to sample?

Accepted Answer

A)  109 
B)  80 
C)  79 
D)  62 
E)  9 
A)  109 
B)  80 
C)  79 
D)  62 
E)  9

Question 19

As standard deviation increases, sample size ________ to achieve a specified level of confidence.

Accepted Answer

A)  increases 
B)  decreases 
C)  remains the same 
A)  increases 
B)  decreases 
C)  remains the same

Question 20

When sample size is 11, find t.10.

Accepted Answer

1.372
df =

The tolerance interval of 95.44 percent is ________ a 95.44 percent confidence interval.

The exact spread of the t distribution depends on the ________.

Which of the following is an advantage of a confidence interval estimate over a point estimate for a population parameter?

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

Researchers studied the role that the age of workers has in determining the hours per month spent on personal tasks. A sample of 1,686 adults were observed for one month. The data follow. Construct an 88 percent confidence interval for the mean hours spent on personal tasks for 18- to 24-year-olds.

A confidence interval increases in width as

What sample size is needed to estimate with 95 percent confidence the mean intake of daily calcium within 20 units of the true mean if the intake is normally distributed with a variance of 1900 units?

When sample size is 16, find t_.025.

When the level of confidence and sample size remain the same, a confidence interval for a population proportion, p, will be narrower when (1 − ) is larger than when (1 − )] is smaller.

In a randomly selected group of 650 automobile deaths, 180 were alcohol related. Construct a 95 percent confidence interval for the true proportion of all automobile accidents caused by alcohol.

In a manufacturing process, a random sample of 36 manufactured bolts has a mean length of 3 inches with a standard deviation of .3 inches. What is the 99 percent confidence interval for the true mean length of the manufactured bolt?

In a survey of 1,000 people, 420 are opposed to an income tax increase. Construct a 95 percent confidence interval for the proportion of people in the population opposed to this tax increase.

A sample of 12 items yields = 48.5 grams and s = 1.5 grams. Assuming a normal distribution, construct a 90 percent confidence interval for the population mean weight.

As standard deviation increases, sample size ________ to achieve a specified level of confidence.

When sample size is 11, find t_.10.

An Introduction to Business Statistics and Analytics

Descriptive Statistics and Analytics: Tabular and Graphical Methods

Descriptive Statistics and Analytics: Numerical Methods

Probability and Probability Models

Predictive Analytics I: Trees, K-Nearest Neighbors, Naive Bayes,

Discrete Random Variables

Continuous Random Variables

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 and Model Building

Predictive Analytics Ii: Logistic Regression, Discriminate Analysis,

Time Series Forecasting and Index Numbers

Nonparametric Methods

Decision Theory

Filters

Exam 9: Confidence Intervals

The tolerance interval of 95.44 percent is ________ a 95.44 percent confidence interval.

The exact spread of the t distribution depends on the ________.

Which of the following is an advantage of a confidence interval estimate over a point estimate for a population parameter?

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

Researchers studied the role that the age of workers has in determining the hours per month spent on personal tasks. A sample of 1,686 adults were observed for one month. The data follow. Construct an 88 percent confidence interval for the mean hours spent on personal tasks for 18- to 24-year-olds.

A confidence interval increases in width as

What sample size is needed to estimate with 95 percent confidence the mean intake of daily calcium within 20 units of the true mean if the intake is normally distributed with a variance of 1900 units?

When sample size is 16, find t.025.

When the level of confidence and sample size remain the same, a confidence interval for a population proportion, p, will be narrower when (1 − ) is larger than when (1 − )] is smaller.

In a randomly selected group of 650 automobile deaths, 180 were alcohol related. Construct a 95 percent confidence interval for the true proportion of all automobile accidents caused by alcohol.

In a manufacturing process, a random sample of 36 manufactured bolts has a mean length of 3 inches with a standard deviation of .3 inches. What is the 99 percent confidence interval for the true mean length of the manufactured bolt?

In a survey of 1,000 people, 420 are opposed to an income tax increase. Construct a 95 percent confidence interval for the proportion of people in the population opposed to this tax increase.

A sample of 12 items yields = 48.5 grams and s = 1.5 grams. Assuming a normal distribution, construct a 90 percent confidence interval for the population mean weight.

As standard deviation increases, sample size ________ to achieve a specified level of confidence.

When sample size is 11, find t.10.

An Introduction to Business Statistics and Analytics

Descriptive Statistics and Analytics: Tabular and Graphical Methods

Descriptive Statistics and Analytics: Numerical Methods

Probability and Probability Models

Predictive Analytics I: Trees, K-Nearest Neighbors, Naive Bayes,

Discrete Random Variables

Continuous Random Variables

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 and Model Building

Predictive Analytics Ii: Logistic Regression, Discriminate Analysis,

Time Series Forecasting and Index Numbers

Nonparametric Methods

Decision Theory

Filters

When sample size is 16, find t_.025.

When sample size is 11, find t_.10.