# 5pts Best ontime airlines: Hawaiian Airlines topped the list of the most punctual U.

Question 1

5.5 pts

Best ontime airlines: Hawaiian Airlines topped the list of the most punctual U.S. airlines for full-year 2014, according to data released by the Bureau of Transportation Statistics. The on-time arrival performance was 91.9% Another aviation data service believes that this percentage now is even higher. The team of researchers chose 130 randomly selected flights and find that 120 of the flights arrived on time.

Can a hypothesis test be used to determine whether the proportion of Hawaiian Airlines flights that arrive on-time is higher than 91.9%?

Yes, because the sample is random. Thus, it is representative of the population of flights for the airlines.

Yes, because the sample is random and (130)(0.923) and (130)(0.077) are both at least 10. This means the normal model is a good fit for the sampling distribution.

Yes, because the sample is random and (130)(0.919) and (130)(0.081) are both at least 10. This means the normal model is a good fit for the sampling distribution.

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Question 2

5.5 pts

Researchers conducted a study to determine whether the majority of community college students plan to vote in the next presidential election. They surveyed 650 randomly selected community college students and found that 55% of them plan to vote.

Which of the following are the appropriate null and alternative hypotheses for this research question?

H

0

: p

=

0.50

H

a

: p

0.50

H

0

: p

=

0.50

H

a

: p

>

0.50

H

0

: p

=

0.55

H

a

: p

0.55

H

0

: μ

=

0.55

H

a

: μ

>

0.55

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Question 3

5.5 pts

In survey conducted by Quinnipiac University from October 25-31, 2011, 47% of a sample of 2,294 registered voters approved of the job Barack Obama was doing as president.

What is the 99% confidence interval for the proportion of all registered voters who approved of the job Barack Obama was doing as president?

(0.443, 0.497)

(0.460, 0.480)

(0.453, 0.487)

(0.450, 0.490)

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Question 4

5.5 pts

Concert marketing: The college’s performing arts center wanted to investigate why ticket sales for the upcoming season significantly decreased from last year’s sales. The marketing staff collected data from a survey of community residents. Out of the 110 people surveyed, only 7 received the concert brochure in the mail.

Which of the following is a reason that the marketing staff should not calculate a confidence interval for the proportion of all community residents who received the concert brochure by mail? Check all that apply.

The sample needs to be random, but we don’t know if it is.

The actual count of community residents who received the concert brochure by mail is too small.

The actual count of students who community residents who didn’t receive the concert brochure by mail is too small.

n(p‐hat) is not greater than 10.

n(1 minus p‐hat) is not greater than 10.

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Question 5

5.5 pts

Parking survey: For a class assignment, a group of statistics students set up a table near the student parking lot. They asked students who passed by to complete a quick survey about whether they support the building of a multi-level parking structure that would add 425 new spaces at the college. They used the information from the survey to calculate the 95% confidence interval: (0.53, 0.72). To which population does the confidence interval apply?

They apply to all students at the college.

The results do not apply to any population because this was a convenience sample.

They apply only to the population of those who use the student parking lot.

They apply only to the population of those students who drive to the college.

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Question 6

5.5 pts

A researcher is trying to decide how many people to survey. Which of the following sample sizes will have the smallest margin of error?

500

800

1000

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Question 7

5.5 pts

Academic Advising: In 2014, the Community College Survey of Student Engagement reported that 32% of the students surveyed rarely or never use academic advising services. Since then, a local California community college that participated in the survey hired several new academic counselors and focused on outreach efforts to increase student awareness of available services. The counseling office staff then conducted a survey of 500 randomly selected students at the college, and 26% of those students said that they rarely or never use academic advising services. Campus administrators want to know whether the hiring and outreach efforts increased student use of academic advising. Which alternative hypothesis is appropriate?

The percentage of students at the college who say that they rarely or never use academic advising services is not the same as the percentage reported by the Community College Survey of Student Engagement (32%).

The percentage of students at the college who say that they rarely or never use academic advising services is 26%.

The percentage of students at the college who say that they rarely or never use academic advising services is less than the percentage reported by the Community College Survey of Student Engagement (32%).

The percentage of students at the college who say that they rarely or never use academic advising services is greater than the percentage reported by the Community College Survey of Student Engagement (32%).

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Question 8

5.5 pts

Gun rights vs. gun control: In a December 2014 report, “For the first time in more than two decades of Pew Research Center surveys, there is more support for gun rights than gun control.” According to a Pew Research survey, 52% of Americans say that protecting gun rights is more important than controlling gun ownership. Gun control advocates in an urban city believe that the percentage is lower among city residents and conduct a survey. They test the hypotheses H

0

: p = 0.52 versus H

a

: p < 0.52. They calculate a P‐value of 0.078. Using a significance level of 0.05, which of the following is the best explanation for how to use the P‐value to reach a conclusion in this case?

Since the P‐value is greater than the significance level, we reject the null hypothesis.

Since the P‐value is greater than the significance level, we fail to reject the null hypothesis.

Since the P‐value is greater than the significance level, we accept the null hypothesis.

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Question 9

5.5 pts

According to a Gallup survey conducted in July 2011, 20% of Americans favor reducing the U.S. budget deficit by using spending cuts only, with no tax increases. An economics professor believes that fewer college students would favor deficit reduction through spending cuts only.

The professor surveys 500 college students and finds that 75 of them favor reducing the deficit using only spending cuts. What is the test statistic?

Z

=

2.80

Z

=

2.80

Z

=

2.80

Z

=

2.80

Z

=

3.13

Z

=

3.13

Z

=

3.13

Z

=

3.13

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Question 10

5.5 pts

Sexual assault in college: In a Washington Post/Kaiser Family Foundation poll conducted from January through March 2015, 46% of adults (ages 17‐26) who attended college during the past 4 years say it’s unclear whether sexual activity when both people have not given explicit agreement is sexual assault. The survey methodology section states that the margin of error is ±3.5% at the 95% confidence level.

What does this margin of error tell you about the results of this poll?

We are 95% confident that the sample proportion is off by 3.5%.

We are confident that 95% of the responses are within 3.5% of the population proportion.

We are 95% confident that the population proportion is within 3.5% of the sample proportion of 46%.

We are confident that population proportion is within 3.5% of the sample proportion of 46%.

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Question 11

5.5 pts

College alcohol and drug use: In a Washington Post/Kaiser Family Foundation poll conducted from January through March 2015, 56% of adults (ages 17‐26) who attended college during the past 4 years say that alcohol and drug use at their school is a big problem. The 95% confidence interval is (0.53, 0.59).

Which of the following is an appropriate interpretation of the 95% confidence interval?

There is a 95% probability that the proportion of adults (ages 17‐26) who attended college during the past 4 years say that alcohol and drug use at their school is a big problem is between 53% and 59%.

We are 95% confident that the proportion of the sample who say that alcohol and drug use at their school is a big problem is between 53% and 59%.

Of random samples of the same size, 95% will have between 53% and 59% of respondents who say that alcohol and drug use at their school is a big problem.

We are 95% confident that the proportion of adults (ages 17‐26) who attended college during the past 4 years and say that alcohol and drug use at their school is a big problem is between 53% and 59%.

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Question 12

5.5 pts

Privacy issues: In a Fall 2014 Pew Research survey, 25% of American adults say they are “not at all confident” that the records of their activity maintained by credit card companies will remain private and secure. With numerous data breaches since then, a consumer group is interested in determining whether the proportion has increased this year. They select a random sample of 300 adults and find that 30% state they are not at all confident.

After conducting the hypothesis test for p = 0.25 compared to p > 0.25, we obtain a P‐value of 0.023. Which of the following interpretations of the P‐value is correct?

There is a 2.3% chance that 25% of American adults say they are not at all confident that the records of their activity maintained by credit card companies will remain private and secure.

There is a 2.3% chance that 30% of American adults say they are not at all confident that the records of their activity maintained by credit card companies will remain private and secure.

There is a 2.3% chance that 30% or more of American adults say they are not at all confident that the records of their activity maintained by credit card companies will remain private and secure if we assume 25% of American adults are not at all confident in 2014.

There is a 2.3% chance that 30% or more of a sample of 300 American adults say they are not at all confident that the records of their activity maintained by credit card companies will remain private and secure if 25% of Americans are not at all confident this year.

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Question 13

5.5 pts

Texting while driving: The accident rate for students who didn’t text while using a driving simulator was 7%. In a driver distraction study of 1,876 randomly selected students, the accident rate for students who texted while driving was higher than 7%. This difference was statistically significant at the 0.05 level.

Which of the following best describes how we should interpret these results?

Because of the large size of the sample, these results are strong evidence that texting accounts for a much larger proportion of accidents in the population of student drivers.

With a large sample, statistically significant results may actually be only a small improvement over the control group (depending on the size of the increase in percentages).

With a large sample, statistically significant results suggest a large increase in the accident rate for the texting group over the control group.

Regardless of the sample size, a statistically significant result means there is a meaningful difference in the accident rates for the two groups.

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Question 14

5.5 pts

One population proportion test: Which of the following situations involves testing a claim about a single population proportion?

The Centers for Disease Control estimates that 22.8% of Americans (ages 18 to 24) get 6 or less hours of sleep per night. A researcher believes that the figure for college students is higher than this.

The mean SAT math score for Florida is 514. An educational researcher is concerned that this average may be lower in rural counties.

A Statistics student wants to determine whether there is a difference in the average number of credit hours male and female students are taking.

A growing practice among some parents is called “redshirting,” Redshirting means holding a child back a year from starting kindergarten even though he or she is eligible by age. Many states use August 31 as the cutoff for the 5th birthday in order for a child to start kindergarten. A researcher is curious if the proportion of boys with August birthdays who are redshirted is different than the proportion of girls with August birthdays who are redshirted.

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Question 15

5.5 pts

Gender and College Students: According to the U.S. Department of Education, approximately 57% of students attending colleges in the U.S. are female. A statistics student is curious whether this is true at her college. She tests the hypotheses H0: p = 0.57 versus Ha: p ≠ 0.57.

The P‐value is not small enough to reject the null hypothesis. Which of the following is an appropriate conclusion?

There is enough evidence to say that the proportion of female students at the college is different from 0.57.

There is not enough evidence to say that the proportion of female students at the college is different from 0.57.

There is enough evidence to say that the proportion of female students at the college is equal to the national figure of 57%.

The probability that the proportion of female students at the college is different from 0.57 is equal to the level of significance, 0.05.

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Question 16

6 pts

The trustees of a local school district commission a survey to determine voter opinions about a possible bond measure to fund school upgrades. In a poll of 293 of the district’s 5,019 registered voters, 178 would support the bond measure.

Conduct a hypothesis test to determine if such a bond would pass with the required 55% of the vote. Use a 5% significance level to make your decision.

Use the applet (at the top of this Checkpoint) to determine the P‐value.

Which of the following is an appropriate conclusion based on the results?

This poll suggests that the bond measure will pass with over 60% support from the voters in the district.

Over 60% of the people polled support the bond measure, but this is not strong enough evidence to conclude that the bond measure has the required 55% support in the district.

This poll provides strong evidence that the bond measure will pass.

This poll suggests that 55% of the district will support the bond measure.

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Question 17

6 pts

Suppose that only 40% of the U.S. public supported the general direction of the previous U.S. President’s policies. To determine whether support for the current President is higher than 40%, a major polling organization conducts a poll with a random sample. Of the 500 in the sample, 210 support the current President’s policies.

Conduct a hypothesis test to determine if support for the current President’s policies is greater than 40%. Use a 5% significance level to make your decision.

Use the applet (at the top of this Checkpoint) to determine the P‐value.

Which of the following is an appropriate conclusion based on the results?

This poll provides strong evidence that support for the current President’s policies is greater than 40%.

This poll suggests that support for the current President’s policies is higher than 40%, but the increase is not statistically significant.

From this poll we can conclude that 42% of the U.S. public supports the general direction of the current President’s policies.

From this poll we can conclude that 40% of the U.S. public supports the general direction of the current President’s policies.

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Question 18

5.5 pts

Gender and College Students: According to the U.S. Department of Education, approximately 57% of students attending colleges in the U.S. are female. A statistics student is curious whether this is true at her college. She tests the hypotheses H0: p = 0.57 versus Ha: p ≠ 0.57.

She plans to use a significance level of 0.05. She calculates her test statistic to be 1.42.

Using the applet (at the top of this Checkpoint), what is the P‐value?

P‐value = 0.078

P‐value = 0.156

P‐value = 0.922

P‐value = 0.05