Question 1

Suzie has installed a new spam blocker program on her email.She used to receive an average of 20 spam emails a day.Is the new program working?

Accepted Answer

A)   
B)   
C)   
D)   
E)   
A)   
B)   
C)   
D)   
E)

Question 2

Students investigating the packaging of chocolate chip cookies purchased 10 450-gram bags of a particular brand.They carefully weighed the contents of each bag,recording the following weights (in grams): 467.6,427.9,464.8,447.8,447.8,456.3,459.1,444.9,439.3,450.6.The students plan to test the hypothesis that the mean weight agrees with the company's stated weight on each bag.Decide whether or not the conditions and assumptions for inference with a t-test are satisfied.Explain your answer.

Accepted Answer

The data probably comprise a random samp

Question 3

You want to estimate the average gas price in your city for a litre of regular unleaded gasoline with 90% confidence.You believe that the standard deviation of prices is $0.04.If you wish to achieve a margin of error no larger than $0.02,how many gas stations should you sample?

Accepted Answer

A) 13 
B) 11 
C) 12 
D) 14 
E) 10 
A) 13 
B) 11 
C) 12 
D) 14 
E) 10

Question 4

The amounts (in millilitres)of juice in eight randomly selected juice bottles are:  
Construct a 98% confidence interval for the mean amount of juice in all such bottles.

Accepted Answer

A) (468.09,471.05) 
B) (441.48,471.05) 
C) (443.28,468.96) 
D) (468.09,482.22) 
E) (441.48,468.09) 
A) (468.09,471.05) 
B) (441.48,471.05) 
C) (443.28,468.96) 
D) (468.09,482.22) 
E) (441.48,468.09)

Question 5

The owner of a football team claims that the average attendance at games is over 74,100,and he is therefore justified in moving the team to a city with a larger stadium.An independent investigator will conduct a hypothesis test to determine whether his claim is accurate.

Accepted Answer

A) Upper-tailed 
B) Two-sided 
C) Lower-tailed 
A) Upper-tailed 
B) Two-sided 
C) Lower-tailed

Question 6

A credit union took a random sample of 40 accounts and obtained the following 90% confidence interval for the mean checking account balance at the institution: $2,193 < μ(balance)< $3,828.

Accepted Answer

A) We are 90% confident that the mean checking account balance in the U.S.is between $2,193 and $3,828. 
B) About 9 out of 10 people have a checking account balance between $2,193 and $3,828. 
C) If we took random samples of checking accounts at this credit union,about nine out of ten of them would produce this confidence interval. 
D) We are 90% confident that the mean checking account balance at this credit union is between $2,193 and $3,828,based on this sample. 
E) We are 90% sure that the mean balance for checking accounts in the sample was between $2,193 and $3,828. 
A) We are 90% confident that the mean checking account balance in the U.S.is between $2,193 and $3,828. 
B) About 9 out of 10 people have a checking account balance between $2,193 and $3,828. 
C) If we took random samples of checking accounts at this credit union,about nine out of ten of them would produce this confidence interval. 
D) We are 90% confident that the mean checking account balance at this credit union is between $2,193 and $3,828,based on this sample. 
E) We are 90% sure that the mean balance for checking accounts in the sample was between $2,193 and $3,828.

Question 7

A one-sample t-test for a the mean population score on an aptitude test is performed.The hypotheses are:  
The computer test statistic,t,i s positive,and the P-value for the test is found to be 0.07.What is a correct interpretation of this P-value?

Accepted Answer

A) If the null hypothesis were true,the probability of observing the test statistic would be 0.07. 
B) If the null hypothesis were true,the observed sample values would occur 7% of the time. 
C) Reject the null.At a significance level of 0.05,there is strong evidence that the mean aptitude score is different from 100. 
D) If the null hypothesis were true,the probability of observing a value of the test statistic as large or larger than that observed would be 0.07. 
E) If the null hypothesis were true,the probability of observing a value of the test statistic as extreme or more extreme than actually observed would be 0.07. 
A) If the null hypothesis were true,the probability of observing the test statistic would be 0.07. 
B) If the null hypothesis were true,the observed sample values would occur 7% of the time. 
C) Reject the null.At a significance level of 0.05,there is strong evidence that the mean aptitude score is different from 100. 
D) If the null hypothesis were true,the probability of observing a value of the test statistic as large or larger than that observed would be 0.07. 
E) If the null hypothesis were true,the probability of observing a value of the test statistic as extreme or more extreme than actually observed would be 0.07.

Question 8

Analysis of a random sample of 250 Nova Scotia nurses produced a 95% confidence interval for the mean annual salary of $42,807 < μ(Nurse Salary)< $49,699.

Accepted Answer

A) About 95% of Nova Scotia nurses earn between $42,807 and $49,699. 
B) We are 95% confident that the average nurse salary in the Canada is between $42,807 and $49,699. 
C) About 95% of the nurses surveyed earn between $42,807 and $49,699. 
D) We are 95% confident that the interval from $42,807 to $49,699 contains the true mean salary of all Nova Scotia nurses. 
E) If we took many random samples of Nova Scotia nurses,about 95% of them would produce this confidence interval. 
A) About 95% of Nova Scotia nurses earn between $42,807 and $49,699. 
B) We are 95% confident that the average nurse salary in the Canada is between $42,807 and $49,699. 
C) About 95% of the nurses surveyed earn between $42,807 and $49,699. 
D) We are 95% confident that the interval from $42,807 to $49,699 contains the true mean salary of all Nova Scotia nurses. 
E) If we took many random samples of Nova Scotia nurses,about 95% of them would produce this confidence interval.

Question 9

You want to see if the number of minutes cell phone users use each month has changed from its mean of 120 minutes 2 years ago.You take a random sample of 100 cell phone users and find an average of 135 minutes used.

Accepted Answer

A)   
B)   
C)   
D)   
E)   
A)   
B)   
C)   
D)   
E)

Question 10

A test of sobriety involves measuring the subject's motor skills.Twenty randomly selected sober subjects take the test and produce a mean score of 41.0 with a standard deviation of 3.4.At a significance level of 0.01,test the claim that the true mean score for all sober subjects is equal to 39.0.

Accepted Answer

A) Reject the null hypothesis of μ = 39.0 with a P-value of 0.00823.There is strong evidence that the true mean score for sober subjects is not 39.0. 
B) Reject the null hypothesis of μ = 39.0 with a P-value of 0.01647.There is sufficient evidence that the true mean score for sober subjects is different from 39.0. 
C) Fail to reject the null hypothesis of μ = 39.0 with a P-value of 0.01647.There is not sufficient evidence that the true mean score for sober subjects is different from 39.0. 
D) Fail to reject the null hypothesis of μ = 39.0 with a P-value of 0.02647.There is not sufficient evidence that the true mean score for sober subjects is different from 39.0. 
E) There is not enough information to perform the test. 
A) Reject the null hypothesis of μ = 39.0 with a P-value of 0.00823.There is strong evidence that the true mean score for sober subjects is not 39.0. 
B) Reject the null hypothesis of μ = 39.0 with a P-value of 0.01647.There is sufficient evidence that the true mean score for sober subjects is different from 39.0. 
C) Fail to reject the null hypothesis of μ = 39.0 with a P-value of 0.01647.There is not sufficient evidence that the true mean score for sober subjects is different from 39.0. 
D) Fail to reject the null hypothesis of μ = 39.0 with a P-value of 0.02647.There is not sufficient evidence that the true mean score for sober subjects is different from 39.0. 
E) There is not enough information to perform the test.

Question 11

P-value for t ≤ 2.13 for a sample of size 31

Accepted Answer

A) 0.9913 
B) 0.0207 
C) 0.9480 
D) 0.9793 
E) 0.9653 
A) 0.9913 
B) 0.0207 
C) 0.9480 
D) 0.9793 
E) 0.9653

Question 12

In the past,the mean battery life for a certain type of flashlight battery has been 8.8 hours.The manufacturer has introduced a change in the production method and wants to perform a hypothesis test to determine whether the mean battery life has increased as a result.The hypotheses are:  
Explain the result of a Type I error.

Accepted Answer

A) The manufacturer will decide the mean battery life is 8.8 hours when in fact it is greater than 8.8 hours. 
B) The manufacturer will decide the mean battery life is 9.6 hours greater than it was prior to the change in the production method. 
C) The manufacturer will decide the mean battery life is 9.6 hours lower than it was prior to the change in the production method. 
D) The manufacturer will decide the mean battery life is greater than 8.8 hours when in fact it is greater than 8.8 hours . 
E) The manufacturer will decide the mean battery life is greater than 8.8 hours when in fact it is 8.8 hours. 
A) The manufacturer will decide the mean battery life is 8.8 hours when in fact it is greater than 8.8 hours. 
B) The manufacturer will decide the mean battery life is 9.6 hours greater than it was prior to the change in the production method. 
C) The manufacturer will decide the mean battery life is 9.6 hours lower than it was prior to the change in the production method. 
D) The manufacturer will decide the mean battery life is greater than 8.8 hours when in fact it is greater than 8.8 hours . 
E) The manufacturer will decide the mean battery life is greater than 8.8 hours when in fact it is 8.8 hours.

Question 13

The principal of a high school randomly selected 30 students to take a math test.Of the 30 students who wrote the test,19 scored more than 75%,4 scored exactly 75%,and 7 scored below 75%.Perform a sign test to determine if the median score is greater than 50% using a 1% level of significance.

Accepted Answer

@#IMG-DLM&_TB3448_11 
: The median test score is 7

Question 14

P-value for t ≥ 2.13 for a sample of size 31

Accepted Answer

A) 0.0520 
B) 0.0207 
C) 0.9793 
D) 0.0087 
E) 0.0347 
A) 0.0520 
B) 0.0207 
C) 0.9793 
D) 0.0087 
E) 0.0347

Question 15

A manufacturer produces refrigerators that are claimed to maintain a true mean temperature of 7°C,ideal for certain beverages.The owner of a beverage company wants to conduct a test to determine if the true mean temperature of the refrigerators is different from this value.

Accepted Answer

A) Upper-tailed 
B) Lower-tailed 
C) Two-sided 
A) Upper-tailed 
B) Lower-tailed 
C) Two-sided

Question 16

You have constructed a 95% confidence interval to estimate the mean number of people downloading music files from the internet using a sample of 150 people.Which of the following statements are true?
I.A 95% Confidence interval will be wider than a 99% confidence interval.
II.Sampling a smaller number of people will increase the margin of error.
III.Changing the sample size will change the value of  
.

Accepted Answer

A) I,II,III 
B) I,II 
C) I 
D) II 
E) II,III 
A) I,II,III 
B) I,II 
C) I 
D) II 
E) II,III

Question 17

Alarmed at the rising gas prices in your town,you decide to estimate the average gas price for a litre of regular unleaded gasoline.From your sample of 25 gas stations,you calculate a 90% confidence interval of ($1.33,$1.41)

Accepted Answer

A) $0.08 
B) $1.37 
C) $0.04 
D) $2.74 
E) Not enough information is given. 
A) $0.08 
B) $1.37 
C) $0.04 
D) $2.74 
E) Not enough information is given.

Question 18

P-value for |t| > 1.76 with 24 degrees of freedom

Accepted Answer

A) 0.0781 
B) 0.1562 
C) 0.0911 
D) 0.9544 
E) 0.0456 
A) 0.0781 
B) 0.1562 
C) 0.0911 
D) 0.9544 
E) 0.0456

Question 19

98% confidence interval with df = 20

Accepted Answer

A) 2.518 
B) 1.325 
C) 2.539 
D) 2.330 
E) 2.528 
A) 2.518 
B) 1.325 
C) 2.539 
D) 2.330 
E) 2.528

Question 20

A quality control manager at a bottling plant wishes to know if the median amount of juice in their 473 mL bottles actually falls below 473 mL.The amounts of juice in 34 randomly selected juice bottles are measured.Of the 34 bottles,21 contained less than 473 mL,4 contained exactly 473 mL,and 9 contained more 473 mL.Perform a sign test to determine if the median amount is less than 473 mL.Use a 5% level of significance.

Accepted Answer

@#IMG-DLM&_TB3448_11 
: The median amount per bott

Exam 22: Inferences About Means

Suzie has installed a new spam blocker program on her email.She used to receive an average of 20 spam emails a day.Is the new program working?

You want to estimate the average gas price in your city for a litre of regular unleaded gasoline with 90% confidence.You believe that the standard deviation of prices is $0.04.If you wish to achieve a margin of error no larger than $0.02,how many gas stations should you sample?

The amounts (in millilitres)of juice in eight randomly selected juice bottles are: Construct a 98% confidence interval for the mean amount of juice in all such bottles.

The owner of a football team claims that the average attendance at games is over 74,100,and he is therefore justified in moving the team to a city with a larger stadium.An independent investigator will conduct a hypothesis test to determine whether his claim is accurate.

A credit union took a random sample of 40 accounts and obtained the following 90% confidence interval for the mean checking account balance at the institution: $2,193 < μ(balance)< $3,828.

A one-sample t-test for a the mean population score on an aptitude test is performed.The hypotheses are: The computer test statistic,t,i s positive,and the P-value for the test is found to be 0.07.What is a correct interpretation of this P-value?

Analysis of a random sample of 250 Nova Scotia nurses produced a 95% confidence interval for the mean annual salary of $42,807 < μ(Nurse Salary)< $49,699.

You want to see if the number of minutes cell phone users use each month has changed from its mean of 120 minutes 2 years ago.You take a random sample of 100 cell phone users and find an average of 135 minutes used.

A test of sobriety involves measuring the subject's motor skills.Twenty randomly selected sober subjects take the test and produce a mean score of 41.0 with a standard deviation of 3.4.At a significance level of 0.01,test the claim that the true mean score for all sober subjects is equal to 39.0.

P-value for t ≤ 2.13 for a sample of size 31

The principal of a high school randomly selected 30 students to take a math test.Of the 30 students who wrote the test,19 scored more than 75%,4 scored exactly 75%,and 7 scored below 75%.Perform a sign test to determine if the median score is greater than 50% using a 1% level of significance.

P-value for t ≥ 2.13 for a sample of size 31

A manufacturer produces refrigerators that are claimed to maintain a true mean temperature of 7°C,ideal for certain beverages.The owner of a beverage company wants to conduct a test to determine if the true mean temperature of the refrigerators is different from this value.

Alarmed at the rising gas prices in your town,you decide to estimate the average gas price for a litre of regular unleaded gasoline.From your sample of 25 gas stations,you calculate a 90% confidence interval of ($1.33,$1.41)

P-value for |t| > 1.76 with 24 degrees of freedom

98% confidence interval with df = 20

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