Questions and Answers of Practice of Statistics

A study of child care enrolled 1364 infants and followed them through their sixth year in school. Later, the researchers published an article in which they stated that “the more time children spent
An educator wants to compare the effectiveness of computer software for teaching biology with that of a textbook presentation. She gives a biology pretest to each student in a group of high school
Is fish good for the gut? Researchers tracked 22,000 male physicians for 22 years. Those who reported eating seafood of any kind at least 5 times per week had a 40% lower risk of colon cancer than
Some Internet service providers (ISPs) charge companies based on how much bandwidth they use in a month. One method that ISPs use to calculate bandwidth is to find the 95th percentile of a
Does the type of program people watch influence how much they eat? A total of 94 college students were randomly assigned to one of three treatments: watching 20 minutes of a Hollywood action movie
A study by Pamela Herd of the University of Wisconsin–Madison found a link between high school grades and health. Analyzing data from the Wisconsin Longitudinal Study, which has tracked the lives
A simple random sample of 1200 adult Americans is selected, and each person is asked the following question: “In light of the huge national deficit, should the government at this time spend
How many points do turnovers cost teams in the NFL? The scatterplot shows the relationship between x = number of turnovers and y = number of points scored by teams in the NFL during 2015, along with
Suppose that 35% of the voters in a state are registered as Republicans, 40% as Democrats, and 25% as Independents. A newspaper wants to select a sample of 1000 registered voters to predict the
A local news agency conducted a survey about unemployment by randomly dialing phone numbers during the work day until it gathered responses from 1000 adults in its state. In the survey, 19% of those
Your statistics class has 30 students. You want to ask an SRS of 5 students from your class whether they use a mobile device for the online quizzes. You label the students 01, 02, … , 30. You enter
To gather information about the validity of a new standardized test for 10th-grade students in a particular state, a random sample of 15 high schools was selected from the state. The new test was
Comment on each of the following as a potential sample survey question. Is the question clear? Is it slanted toward a desired response?a. Which of the following best represents your opinion on gun
A popular website places opinion poll questions next to many of its news stories. Simply click your response to join the sample. One of the questions was “Do you plan to diet this year?” More
Comment on each of the following as a potential sample survey question. Is the question clear? Is it slanted toward a desired response?a. “Some cell phone users have developed brain cancer. Should
Marcos asked a random sample of 50 mall shoppers for their weight. Twenty-five of the shoppers were asked directly and the other 25 were asked anonymously by means of a “secret ballot.” The mean
Two female statistics students asked a random sample of 60 high school boys if they have ever cried during a movie. Thirty of the boys were asked directly and the other 30 were asked anonymously by
A study in El Paso, Texas, looked at seat belt use by drivers. Drivers were observed at randomly chosen convenience stores. After they left their cars, they were invited to answer questions that
An SRS of 880 drivers was asked: “Recalling the last ten traffic lights you drove through, how many of them were red when you entered the intersections?” Of the 880 respondents, 171 admitted that
A survey of drivers began by randomly sampling from all listed residential telephone numbers in the United States. Of 45,956 calls to these numbers, 5029 were completed. The goal of the survey was to
A news organization wants to know what percent of U.S. residents support a “pathway to citizenship” for people who live in the United States illegally. The news organization randomly selects
A total of 300 people participated in a free 12-week weight-loss course at a community health clinic. After one year, administrators emailed each of the 300 participants to see how much weight they
The director of student life at a small college wants to know what percent of students eat regularly in the cafeteria. To find out, the director selects an SRS of 300 students who live in the dorms.
A lumber company wants to estimate the proportion of trees in a large forest that are ready to be cut down. They use an aerial map to divide the forest into 200 equal-sized rectangles. Then they
Laying fiber-optic cable is expensive. Cable companies want to make sure that if they extend their lines to less dense suburban or rural areas, there will be sufficient demand so the work will be
A hotel has 30 floors with 40 rooms per floor. The rooms on one side of the hotel face the water, while rooms on the other side face a golf course. There is an extra charge for the rooms with a water
Michigan Stadium, also known as “The Big House,” seats over 100,000 fans for a football game. The University of Michigan Athletic Department wants to survey fans about concessions that are sold
At a party, there are 30 students over age 21 and 20 students under age 21. You choose at random 3 of those over 21 and separately choose at random 2 of those under 21 to interview about their
A corporation employs 2000 male and 500 female engineers. A stratified random sample of 200 male and 50 female engineers gives every individual in the population the same chance to be chosen for the
The director of student life at a university wants to estimate the proportion of undergraduate students who regularly park a car on campus. Describe how to select a stratified random sample of
Suppose 1000 iPhones are produced at a factory today. Management would like to ensure that the phones’ display screens meet their quality standards before shipping them to retail stores. Because it
The owner of a large restaurant is considering a new “no tipping” policy and wants to survey a sample of employees. The policy would add 20% to the cost of food and beverages and the additional
On the west side of Rocky Mountain National Park, many mature pine trees are dying due to infestation by pine beetles. Scientists would like to use sampling to estimate the proportion of all pine
The local genealogical society in Coles County, Illinois, has compiled records on all 55,914 gravestones in cemeteries in the county for the years 1825 to 1985. Historians plan to use these records
To gather data on a 1200-acre pine forest in Louisiana, the U.S. Forest Service laid a grid of 1410 equally spaced circular plots over a map of the forest. A ground survey visited a sample of 10% of
You are planning a report on apartment living in a college town. You decide to select three apartment complexes at random for in-depth interviews with residents.a. Explain how you would use a line of
You want to ask a sample of high school students the question “How much do you trust information about health that you find on the Internet—a great deal, somewhat, not much, or not at all?” You
Many websites include customer reviews of products, restaurants, hotels, and so on. The manager of a hotel was upset to see that 26% of reviewers on a travel website gave the hotel “1 star”—the
Parade magazine posed the following question: “Should drivers be banned from using all cell phones?” Readers were encouraged to vote online at parade.com. The subsequent issue of Parade reported
You may have seen the mall interviewer, clipboard in hand, approaching people passing by. Explain why even a large sample of mall shoppers would not provide a trustworthy estimate of the current
You are on the staff of a member of Congress who is considering a bill that would provide government-sponsored insurance for nursing-home care. You report that 1128 letters have been received on the
The band director at a high school wants to estimate the percentage of parents who support a decrease in the budget for fine arts. Because many parents attend the school’s annual musical, the
How much sleep do high school students get on a typical school night? A counselor designed a survey to find out. To make data collection easier, the counselor surveyed the first 100 students to
A department store mails a customer satisfaction survey to people who make credit card purchases at the store. This month, 45,000 people made credit card purchases. Surveys are mailed to 1000 of
A large retailer prepares its customers’ monthly credit card bills using an automatic machine that folds the bills, stuffs them into envelopes, and seals the envelopes for mailing. Are the
In this project, your team will design and conduct an experiment to investigate the effects of response bias in surveys.82 You may choose the topic for your surveys, but you must design your
A high school’s student newspaper plans to survey local businesses about the importance of students as customers. From an alphabetical list of all local businesses, the newspaper staff chooses 150
Researchers in New Zealand interviewed 907 drivers at age 21. They had data on traffic accidents and they asked the drivers about marijuana use. Here are data on the numbers of accidents caused by
An archaeological dig turns up large numbers of pottery shards, broken stone tools, and other artifacts. Students working on the project classify each artifact and assign a number to it. The counts
Suppose that the measurements of arm span and height were converted from centimeters to meters by dividing each measurement by 100. How will this conversion affect the values of r2 and s?a. r2 will
In its recent Fuel Economy Guide, the Environmental Protection Agency (EPA) gives data on 1152 vehicles. There are a number of outliers, mainly vehicles with very poor gas mileage or hybrids with
Suppose that a tall child with arm span 120 cm and height 118 cm was added to the sample used in this study. What effect will this addition have on the correlation and the slope of the least-squares
One child in the Mumbai study had height 59 cm and arm span 60 cm. This child’s residual isa. −3.2 cm.b. −2.2 cm.c. −1.3 cm.d. 3.2 cm.e. 62.2 cm.Measurements on young children in Mumbai,
In addition to the regression line, the report on the Mumbai measurements says that r2 = 0.95. This suggests thata. Although arm span and height are correlated, arm span does not predict height very
By looking at the equation of the least-squares regression line, you can see that the correlation between height and arm span isa. Greater than zero.b. Less than zero.c. 0.93.d. 6.4.e. Can’t tell
Each year, students in an elementary school take a standardized math test at the end of the school year. For a class of fourth-graders, the average score was 55.1 with a standard deviation of 12.3.
Using data from the LPGA tour, a regression analysis was performed using x = average driving distance and y = scoring average. Using the output from the regression analysis shown below, determine the
What is the relationship between rushing yards and points scored in the National Football League? The table gives the number of rushing yards and the number of points scored for each of the 16 games
Which of the following is not a characteristic of the least-squares regression line?a. The slope of the least-squares regression line is always between – 1 and 1.b. The least-squares regression
People with diabetes measure their fasting plasma glucose (FPG, measured in milligrams per milliliter) after fasting for at least 8 hours. Another measurement, made at regular medical checkups, is
Haley, Jeff, and Nathan measured the height (in inches) and vertical jump (in inches) of 74 students at their school. Here is a scatterplot of the data, along with the least squares regression line.
The scatterplot shows the weight (in pounds) and cost (in dollars) of 11 stand mixers. The mixer from Walmart (highlighted in red) was much lighter—and cheaper—than the other mixers.a. Describe
We expect that a baseball player who has a high batting average in the first month of the season will also have a high batting average the rest of the season. Using 66 Major League Baseball players
Some people think that the behavior of the stock market in January predicts its behavior for the rest of the year. Take the explanatory variable x to be the percent change in a stock market index in
We expect that students who do well on the midterm exam in a course will usually also do well on the final exam. Gary Smith of Pomona College looked at the exam scores of all 346 students who took
The mean height of married American women in their early 20s is 64.5 inches and the standard deviation is 2.5 inches. The mean height of married men the same age is 68.5 inches with standard
Kerry and Danielle wanted to investigate whether tapping on a can of soda would reduce the amount of soda expelled after the can has been shaken. For their experiment, they vigorously shook 40 cans
The average temperature (in degrees Fahrenheit) and average wind speed (in miles per hour) were recorded for 365 consecutive days at Chicago’s O’Hare International Airport. Here is computer
Do beavers benefit beetles? Researchers laid out 23 circular plots, each 4 meters in diameter, in an area where beavers were cutting down cottonwood trees. In each plot, they counted the number of
Mentos are dropped into a newly opened bottle of Diet Coke, carbon dioxide is released from the Diet Coke very rapidly, causing the Diet Coke to be expelled from the bottle. To see if using more
A random sample of 195 students was selected from the United Kingdom using the Census At School data selector. The age x (in years) and height y (in centimeters) were recorded for each student. Here
For many people, the women’s figure skating competition is the highlight of the Olympic Winter Games. Scores in the short program x and scores in the free skate y were recorded for each of the 24
In Exercise 44, we summarized the relationship between x = temperature in degrees Fahrenheit and y = chirps per minute for the striped ground cricket, with the regression line ŷ = –0.31 + 0.212x.
In Exercise 43, we summarized the relationship between x = height of a student (in inches) and y = number of steps required to walk the length of a school hallway, with the regression line ŷ =
Refer to Exercise 52. Use technology to create a residual plot. Sketch the residual plot and explain what information it provides.Exercise 52.Here are the 40-yard-dash times (in seconds) and longjump
Refer to Exercise 51. Use technology to create a residual plot. Sketch the residual plot and explain what information it provides.Exercise 51. Is there a relationship between the amount of sugar
Is there a relationship between the amount of sugar (in grams) and the number of calories in movie-theater candy? Here are the data from a sample of 12 types of candy:a. Sketch a scatterplot of the
Here are the 40-yard-dash times (in seconds) and longjump distances (in inches) for a small class of 12 students:a. Sketch a scatterplot of the data using dash time as the explanatory variable.b. Use
Refer to Exercise 48. Use the equation of the least-squares regression line and the residual plot to estimate the actual fuel consumption of the car when driving 20 kilometers per hour. Exercise
Refer to Exercise 47. Use the equation of the leastsquares regression line and the residual plot to estimate the actual mean weight of the infants when they were 1 month old.Exercise 47.A study of
A study of nutrition in developing countries collected data from the Egyptian village of Nahya. Researchers recorded the mean weight (in kilograms) for 170 infants in Nahya each month during their
Exercise 9 (page 171) gives data on the fuel consumption y of a car at various speeds x. Fuel consumption is measured in liters of gasoline per 100 kilometers driven, and speed is measured in
Exercises 6 and 12, you described the relationship between fat (in grams) and the number of calories in products sold at Starbucks. The scatterplot shows this relationship, along with two regression
In Exercises 5 and 11, you described the relationship between height (in inches) and weight (in pounds) for Olympic track and field athletes. The scatterplot shows this relationship, along with two
The scatterplot shows the relationship between x = temperature in degrees Fahrenheit and y = chirps per minute for the striped ground cricket, along with the regression line ŷ = −0.31+0.212x.
The scatterplot shows the relationship between x = height of a student (in inches) and y = number of steps required to walk the length of a school hallway, along with the regression line ŷ
Refer to Exercise 38.a. Interpret the slope of the regression line.b. Does the value of the y intercept have meaning in this context? If so, interpret the y intercept. If not, explain why.Exercise
Refer to Exercise 37.a. Interpret the slope of the regression line.b. Does the value of the y intercept have meaning in this context? If so, interpret the y intercept. If not, explain why.Exercise
Refer to Exercise 38. During March, the average temperature was 46.4°F and Joan used an average of 490 cubic feet of gas per day. Calculate and interpret the residual for this month.Exercise 38.Joan
Refer to Exercise 37. The Chicago Cubs won the World Series in 2016. They had 103 wins and spent $182 million on payroll. Calculate and interpret the residual for the Cubs.Exercise 37.Earlier we
Joan is concerned about the amount of energy she uses to heat her home. The scatterplot shows the relationship between x = mean temperature in a particular month and y = mean amount of natural gas
Earlier we investigated the relationship between x = payroll (in millions of dollars) and y = number of wins for Major League Baseball teams in 2016. Here is a scatterplot of the data, along with the
Fruit flies are used frequently in genetic research because of their quick reproductive cycle. The length of the thorax (in millimeters) for male fruit flies is approximately Normally distributed
Here are the weights (in milligrams) of 58 diamonds from a nodule carried up to the earth’s surface in surrounding rock. These data represent a population of diamonds formed in a single event deep
If we leave out the low outlier, the correlation for the remaining 13 points in the preceding figure is closest toa. −0.95.b. −0.65.c. 0.d. 0.65.e. 0.95.Select the best answer.
The scatterplot shows reading test scores against IQ test scores for 14 fifth-grade children. There is one low outlier in the plot. What effect does this low outlier have on the correlation?a. It
If women always married men who were 2 years older than themselves, what would be the correlation between the ages of husband and wife?a. 2b. 1c. 0.5d. 0e. Can’t tell without seeing the dataSelect
The following graph plots the gas mileage (in miles per gallon) of various cars from the same model year versus the weight of these cars (in thousands of pounds). The points marked with red dots
In a scatterplot of the average price of a barrel of oil and the average retail price of a gallon of gas, you expect to seea. Very little association.b. A weak negative association.c. A strong
You have data for many years on the average price of a barrel of oil and the average retail price of a gallon of unleaded regular gasoline. If you want to see how well the price of oil predicts the

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