Question 1

The sample proportion is always the midpoint of a confidence interval for the population proportion.

Accepted Answer

A) True 
 B)False

Question 2

Which statement is most nearly correct,other things being equal?

Accepted Answer

A)  Doubling the sample size will cut the standard error of the mean in half. 
B)  The standard error of the mean depends on the population size. 
C)  Quadrupling the sample size roughly halves the standard error of the mean. 
D)  The standard error of the mean depends on the confidence level. 
A)  Doubling the sample size will cut the standard error of the mean in half. 
B)  The standard error of the mean depends on the population size. 
C)  Quadrupling the sample size roughly halves the standard error of the mean. 
D)  The standard error of the mean depends on the confidence level.

Question 3

The Student's t distribution is always symmetric and bell-shaped,but its tails lie above the normal.

Accepted Answer

A) True 
 B)False

Question 4

The finite population correction factor (FPCF)can be ignored when the sample size is large relative to the population size.

Accepted Answer

A) True 
 B)False

Question 5

To narrow the confidence interval for π,we can either increase n or decrease the level of confidence.

Accepted Answer

A) True 
 B)False

Question 6

Ersatz Beneficial Insurance wants to estimate the cost of damage to cars due to accidents.The standard deviation of the cost is known to be $200.They want to estimate the mean cost using a 95 percent confidence interval within ± $10.What is the minimum sample size n?

Accepted Answer

A)  1083 
B)  4002 
C)  1537 
D)  2301 
A)  1083 
B)  4002 
C)  1537 
D)  2301

Question 7

Professor York randomly surveyed 240 students at Oxnard University and found that 150 of the students surveyed watch more than 10 hours of television weekly.How many additional students would Professor York have to sample to estimate the proportion of all Oxnard University students who watch more than 10 hours of television each week within ± 3 percent with 99 percent confidence?

Accepted Answer

A)  761 
B)  1001 
C)  1489 
D)  1728 
A)  761 
B)  1001 
C)  1489 
D)  1728

Question 8

Which statement is incorrect? Explain.

Accepted Answer

A)  If p = .50 and n = 100,the standard error of the sample proportion is .05. 
B)  In a sample size calculation for estimating π,it is conservative to assume π = .50. 
C)  If n = 250 and p = .06,we cannot assume normality in a confidence interval for π. 
A)  If p = .50 and n = 100,the standard error of the sample proportion is .05. 
B)  In a sample size calculation for estimating π,it is conservative to assume π = .50. 
C)  If n = 250 and p = .06,we cannot assume normality in a confidence interval for π.

Question 9

To determine a 72 percent level of confidence for a proportion,the value of z is approximately:

Accepted Answer

A)  ± 1.65 
B)  ± 0.77 
C)  ± 1.08 
D)  ± 1.55 
A)  ± 1.65 
B)  ± 0.77 
C)  ± 1.08 
D)  ± 1.55

Question 10

A marketing firm is asked to estimate the percent of existing customers who would purchase a "digital upgrade" to their basic cable TV service.The firm wants 99 percent confidence and an error of ± 5 percent.What is the required sample size (to the next higher integer)?

Accepted Answer

A)  664 
B)  625 
C)  801 
D)  957 
A)  664 
B)  625 
C)  801 
D)  957

Question 11

A highway inspector needs an estimate of the mean weight of trucks crossing a bridge on the interstate highway system.She selects a random sample of 49 trucks and finds a mean of 15.8 tons with a sample standard deviation of 3.85 tons.The 90 percent confidence interval for the population mean is:

Accepted Answer

A)  14.72 to 16.88 tons. 
B)  14.90 to 16.70 tons. 
C)  14.69 to 16.91 tons. 
D)  14.88 to 16.72 tons. 
A)  14.72 to 16.88 tons. 
B)  14.90 to 16.70 tons. 
C)  14.69 to 16.91 tons. 
D)  14.88 to 16.72 tons.

Question 12

In constructing a confidence interval,the finite population correction factor (FPCF)can be ignored if samples of 12 items are drawn from a population of 300 items.

Accepted Answer

A) True 
 B)False

Question 13

The sample proportion is in the middle of the confidence interval for the population proportion:

Accepted Answer

A)  in any sample. 
B)  only if the samples are large. 
C)  only if π is not too far from .50. 
A)  in any sample. 
B)  only if the samples are large. 
C)  only if π is not too far from .50.

Question 14

A sample is taken and a confidence interval is constructed for the mean of the distribution.At the center of the interval is always which value?

Accepted Answer

A)  The sample mean   
B)  The population mean μ 
C)  Neither   nor μ since with a sample anything can happen 
D)  Both   
A)  The sample mean   
B)  The population mean μ 
C)  Neither   nor μ since with a sample anything can happen 
D)  Both

Question 15

The Central Limit Theorem (CLT)implies that:

Accepted Answer

A)  the population will be approximately normal if n ≥ 30. 
B)  repeated samples must be taken to obtain normality. 
C)  the distribution of the mean is approximately normal for large n. 
D)  the mean follows the same distribution as the population. 
A)  the population will be approximately normal if n ≥ 30. 
B)  repeated samples must be taken to obtain normality. 
C)  the distribution of the mean is approximately normal for large n. 
D)  the mean follows the same distribution as the population.

Question 16

The distribution of the sample proportion p = x/n is normal when n ≥ 30.

Accepted Answer

A) True 
 B)False

Question 17

A poll showed that 48 out of 120 randomly chosen graduates of California medical schools last year intended to specialize in family practice.What is the width of a 90 percent confidence interval for the proportion that plan to specialize in family practice?

Accepted Answer

A)  ± .0447 
B)  ± .0736 
C)  ± .0876 
D)  ± .0894 
A)  ± .0447 
B)  ± .0736 
C)  ± .0876 
D)  ± .0894

Question 18

An airport traffic analyst wants to estimate the proportion of daily takeoffs by small business jets (as opposed to commercial passenger jets or other aircraft)with an error of ± 4 percent with 90 percent confidence.What sample size should the analyst use?

Accepted Answer

A)  385 
B)  601 
C)  410 
D)  423 
A)  385 
B)  601 
C)  410 
D)  423

Question 19

Using the conventional polling definition,find the margin of error for a customer satisfaction survey of 225 customers who have recently dined at Applebee's.

Accepted Answer

A)  ± 5.0 percent 
B)  ± 4.2 percent 
C)  ± 7.1 percent 
D)  ± 6.5 percent 
A)  ± 5.0 percent 
B)  ± 4.2 percent 
C)  ± 7.1 percent 
D)  ± 6.5 percent

Question 20

Based on the Rule of Three,if no events occur in n independent trials we can set the upper 95 percent confidence bound at 3/n.

Accepted Answer

A) True 
 B)False

The sample proportion is always the midpoint of a confidence interval for the population proportion.

Which statement is most nearly correct,other things being equal?

The Student's t distribution is always symmetric and bell-shaped,but its tails lie above the normal.

The finite population correction factor (FPCF)can be ignored when the sample size is large relative to the population size.

To narrow the confidence interval for π,we can either increase n or decrease the level of confidence.

Ersatz Beneficial Insurance wants to estimate the cost of damage to cars due to accidents.The standard deviation of the cost is known to be $200.They want to estimate the mean cost using a 95 percent confidence interval within ± $10.What is the minimum sample size n?

Which statement is incorrect? Explain.

To determine a 72 percent level of confidence for a proportion,the value of z is approximately:

A marketing firm is asked to estimate the percent of existing customers who would purchase a "digital upgrade" to their basic cable TV service.The firm wants 99 percent confidence and an error of ± 5 percent.What is the required sample size (to the next higher integer)?

A highway inspector needs an estimate of the mean weight of trucks crossing a bridge on the interstate highway system.She selects a random sample of 49 trucks and finds a mean of 15.8 tons with a sample standard deviation of 3.85 tons.The 90 percent confidence interval for the population mean is:

In constructing a confidence interval,the finite population correction factor (FPCF)can be ignored if samples of 12 items are drawn from a population of 300 items.

The sample proportion is in the middle of the confidence interval for the population proportion:

A sample is taken and a confidence interval is constructed for the mean of the distribution.At the center of the interval is always which value?

The Central Limit Theorem (CLT)implies that:

The distribution of the sample proportion p = x/n is normal when n ≥ 30.

A poll showed that 48 out of 120 randomly chosen graduates of California medical schools last year intended to specialize in family practice.What is the width of a 90 percent confidence interval for the proportion that plan to specialize in family practice?

An airport traffic analyst wants to estimate the proportion of daily takeoffs by small business jets (as opposed to commercial passenger jets or other aircraft)with an error of ± 4 percent with 90 percent confidence.What sample size should the analyst use?

Using the conventional polling definition,find the margin of error for a customer satisfaction survey of 225 customers who have recently dined at Applebee's.

Based on the Rule of Three,if no events occur in n independent trials we can set the upper 95 percent confidence bound at 3/n.

Overview of Statistics

Data Collection

Describing Data Visually

Descriptive Statistics

Probability

Discrete Probability Distributions

Continuous Probability Distributions

One-Sample Hypothesis Tests

Two-Sample Hypothesis Tests

Analysis of Variance

Simple Regression

Multiple Regression

Time-Series Analysis

Chi-Square Tests

Nonparametric Tests

Quality Management

Filters

Exam 8: Sampling Distributions and Estimation

The sample proportion is always the midpoint of a confidence interval for the population proportion.

Which statement is most nearly correct,other things being equal?

The Student's t distribution is always symmetric and bell-shaped,but its tails lie above the normal.

The finite population correction factor (FPCF)can be ignored when the sample size is large relative to the population size.

To narrow the confidence interval for π,we can either increase n or decrease the level of confidence.

Ersatz Beneficial Insurance wants to estimate the cost of damage to cars due to accidents.The standard deviation of the cost is known to be $200.They want to estimate the mean cost using a 95 percent confidence interval within ± $10.What is the minimum sample size n?

Which statement is incorrect? Explain.

To determine a 72 percent level of confidence for a proportion,the value of z is approximately:

A marketing firm is asked to estimate the percent of existing customers who would purchase a "digital upgrade" to their basic cable TV service.The firm wants 99 percent confidence and an error of ± 5 percent.What is the required sample size (to the next higher integer)?

A highway inspector needs an estimate of the mean weight of trucks crossing a bridge on the interstate highway system.She selects a random sample of 49 trucks and finds a mean of 15.8 tons with a sample standard deviation of 3.85 tons.The 90 percent confidence interval for the population mean is:

In constructing a confidence interval,the finite population correction factor (FPCF)can be ignored if samples of 12 items are drawn from a population of 300 items.

The sample proportion is in the middle of the confidence interval for the population proportion:

A sample is taken and a confidence interval is constructed for the mean of the distribution.At the center of the interval is always which value?

The Central Limit Theorem (CLT)implies that:

The distribution of the sample proportion p = x/n is normal when n ≥ 30.

A poll showed that 48 out of 120 randomly chosen graduates of California medical schools last year intended to specialize in family practice.What is the width of a 90 percent confidence interval for the proportion that plan to specialize in family practice?

An airport traffic analyst wants to estimate the proportion of daily takeoffs by small business jets (as opposed to commercial passenger jets or other aircraft)with an error of ± 4 percent with 90 percent confidence.What sample size should the analyst use?

Using the conventional polling definition,find the margin of error for a customer satisfaction survey of 225 customers who have recently dined at Applebee's.

Based on the Rule of Three,if no events occur in n independent trials we can set the upper 95 percent confidence bound at 3/n.

Overview of Statistics

Data Collection

Describing Data Visually

Descriptive Statistics

Probability

Discrete Probability Distributions

Continuous Probability Distributions

One-Sample Hypothesis Tests

Two-Sample Hypothesis Tests

Analysis of Variance

Simple Regression

Multiple Regression

Time-Series Analysis

Chi-Square Tests

Nonparametric Tests

Quality Management

Filters