Chapter 3 Review

Portland Community College serves nearly 73,000 full-time and part-time students in the greater Portland area at four main campuses (SE, Cascade, Sylvania, and RC). Student Affairs would like to know how students get to campus. They randomly select 250 students from each of the four main campus and ask them how they got to classes on campus. The following are the results of their survey:

• Public Tra…

CNN conducted a survey of 500 American adults. 62% of those surveyed answered yes to the question, “Do you favor a law to ban the sale of assault weapons and semiautomatic rifles?” The reported margin of error was $\pm 4\%$.

1. What population is being studied?

2. What is the sample?

3. What type of data is this?

4. Is the 62% reported in the problem an example of a statistic or a parameter?

5. What is the confidence interva…

A survey of 265 PCC students found that 23%, plus or minus 4% prefer to study at the library.

1. What population is being studied?

2. What type of data was collected?

3. Is the reported 23% a statistic or a parameter?

4. What is the margin of error?

5. What is the confidence interval?

6. Explain what the confidence interval tells you.

Identify the sampling method. Just the name will suffice.

1. Researchers select every 5th customer who walks into the store to take a survey.

2. Raffle tickets are distributed and collected in a bag, where they are mixed and ten are drawn for prizes.

3. I asked the shoppers near me in the shoe department what size they wear.

4. An IRS auditor randomly selects 25 taxpayers in each filing status (single, head of ho…

Identify the most relevant source of bias in each situation.

1. An opinion poll is posted on Facebook and Twitter asking how you are most likely to vote for in the next election.

2. Keller Auditorium ask all the people in the front three rows if they enjoyed the Broadway play.

3. To determine opinions on voter support for a downtown farmers market, a surveyor randomly questions people working close to the par…

Identify whether each situation describes an observational study or an experiment. If it is an experiment.

1. Subjects are asked to run a mile and record their time.

2. Fifty students were asked to go to a quiet space in the library to memorize a poem. Fifty students were asked to go to a noisy location in the cafeteria to memorize the poem. Each student recorded how much time it took to memorize the poem…

For the clinical trial of a migraine drug, subjects were randomly divided into two groups. The first received an inert pill, while the second received the test medicine. Patients were not aware of which group they were in. After one month, patients reported how many migraines they experienced.

1. Which is the treatment group?

2. Which is the control group (if there is one)?

3. Is this study blind, double-blin…

In a recent study, 380 high risk adolescents involved in the juvenile justice system were recruited to test an app designed to increase mindfulness and reduce substance use. Participants were randomly and equally assigned to use the app (Rewire) or receive services as usual from the Department of Youth Services. Participants were assessed to determine a baseline for substance use at the beginning…

Suppose you buy a new car whose advertised gas mileage is 35 mpg (miles per gallon). After driving the car for several months, you find that you are getting only 30.4 mpg. You phone the manufacturer and learn that the standard deviation for that model is 1.35 mpg.

1. Find the z-score for the gas mileage of your car.

2. Does it appear that your car is getting unusually low gas mileage? Explain your answer…

This data set is a sample of the average number of minutes per week that a driver is delayed by road congestion in 13 cities:

1. Find the mean and the standard deviation, including units.

2. What is the z-score for the city with an average delay time of 42 hours per week?

3. Is an average delay time of 42 hours per week unusual? Explain using the calculated z-score.