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Stats Data And Models 4th Global Edition Richard D. De Veaux, Paul Velleman, David E. Bock - Solutions
SAT prep Can special study courses actually help raise SAT scores? One organization says that the 30 students they tutored achieved an average gain of 60 points when they retook the test.a) Explain why this does not necessarily prove that the special course caused the scores to go up.b) Propose a
Beetles Hoping to learn how to control crop damage by a certain species of beetle, a researcher plans to test two different pesticides in small plots of corn. A few days after application of the chemicals, he’ll check the number of beetle larvae found on each plant. The researcher wants to know
Shingles A research doctor has discovered a new ointment that she believes will be more effective than the current medication in the treatment of shingles (a painful skin rash). Eight patients have volunteered to participate in the initial trials of this ointment. You are the statistician hired as
Weekend deaths A study published in the New England Journal of Medicine (Aug. 2001) suggests that it’s dangerous to enter a hospital on a weekend. During a 10-year period, researchers tracked over 4 million emergency admissions to hospitals in Ontario, Canada. Their findings revealed that
Gas mileage Do cars get better gas mileage with premium instead of regular unleaded gasoline? It might be possible to test some engines in a laboratory, but we’d rather use real cars and real drivers in real day-to-day driving, so we get 20 volunteers. Design the experiment.
Reading Some schools teach reading using phonics (the sounds made by letters) and others using whole language(word recognition). Suppose a school district wants to know which method works better. Suggest a design for an appropriate experiment.
Healing A medical researcher suspects that giving postsurgical patients large doses of vitamin E will speed their recovery times by helping their incisions heal more quickly. Design an experiment to test this conjecture. Be sure to identify the factors, levels, treatments, response variable, and
Dowsing Before drilling for water, many rural homeowners hire a dowser (a person who claims to be able to sense the presence of underground water using a forked stick.) Suppose we wish to set up an experiment to test one dowser’s ability. We get 26 identical containers, fill some with water, and
Swimming Recently, a group of adults who swim regularly for exercise were evaluated for depression. It turned out that these swimmers were less likely to be depressed than the general population. The researchers said the difference was statistically significant.a) What does “statistically
Wine A 2001 Danish study published in the Archives of Internal Medicine casts significant doubt on suggestions that adults who drink wine have higher levels of “good”cholesterol and fewer heart attacks. These researchers followed a group of individuals born at a Copenhagen hospital between 1959
Contrast Baths Contrast bath treatments use the immersion of an injured limb alternately in water of two contrasting temperatures. Those who use the method claim that it can reduce swelling.Researchers compared three treatments:(1) contrast baths and exercise, (2) contrast baths alone, and (3)
Mozart Will listening to a Mozart piano sonata make you smarter? In a 1995 study published in the journal Psychological Science, Rauscher, Shaw, and Ky reported that when students were given a spatial reasoning section of a standard IQ test, those who listened to Mozart for 10 minutes improved
Diet and blood pressure An experiment showed that subjects fed the DASH diet were able to lower their blood pressure by an average of 6.7 points compared to a group fed a “control diet.” All meals were prepared by dieticians.a) Why were the subjects randomly assigned to the diets instead of
Hamstrings Exercise 33 discussed an experiment to see if the time it took athletes with hamstring injuries to be able to return to sports was different depending on which of two exercise programs they engaged in.a) Explain why it was important to assign the athletes to the two different treatments
Swimsuits A swimsuit manufacturer wants to test the speed of its newly designed suit. The company designs an experiment by having 6 randomly selected Olympic swimmers swim as fast as they can with their old swimsuit first and then swim the same event again with the new, expensive swimsuit. The
Shoes A running-shoe manufacturer wants to test the effect of its new sprinting shoe on 100-meter dash times. The company sponsors 5 athletes who are running the 100-meter dash in the 2012 Summer Olympic games. To test the shoe, it has all 5 runners run the 100-meter dash with a competitor’s shoe
Tomatoes II Describe a strategy to randomly split 24 tomato plants into the three groups for the completely randomized single factor experiment of Exercise 4.
Injuries Exercise 33 describes an experiment that studies hamstring injuries. Describe a strategy to randomly assign injured athletes to the two exercise programs. What should be done if one of the athletes says he’d prefer the other program?
Insomnia, at last Exercises 24, 36, and 38 describe an experiment investigating the effectiveness of exercise in combating insomnia. Suppose some of the 40 subjects had maintained a healthy weight, but others were quite overweight. Why might researchers choose to block the subjects by weight level
Omega-3, finis Exercises 21, 35, and 37 describe an experiment investigating the effectiveness of omega-3 fats in treating bipolar disorder. Suppose some of the 30 subjects were very active people who walked a lot or got vigorous exercise several times a week, while others tended to be more
Insomnia, again Exercises 24 and 36 describe an experiment investigating the effectiveness of exercise in combating insomnia. Researchers randomly assigned half of the 40 volunteers to an exercise program.a) Why was it important to randomize in deciding who would exercise?b) What would be the
Omega-3, revisited Exercises 21 and 35 describe an experiment investigating a dietary approach to treating bipolar disorder. Researchers randomly assigned 30 subjects to two treatment groups, one group taking a high dose of omega-3 fats and the other a placebo.a) Why was it important to randomize
Insomnia Exercise 24 describes an experiment showing that exercise helped people sleep better. The experiment involved other groups of subjects who didn’t exercise.Why didn’t the experimenters just have everyone exercise and see if their ability to sleep improved?
Omega-3 Exercise 21 describes an experiment that showed that high doses of omega-3 fats might be of benefit to people with bipolar disorder. The experiment involved a control group of subjects who received a placebo.Why didn’t the experimenters just give everyone the omega-3 fats to see if they
Pew Research compared respondents to an ordinary 5-day telephone survey with respondents to a 4-monthlong rigorous survey designed to generate the highest possible response rate. They were especially interested in identifying any variables for which those who responded to the ordinary survey were
Athletes who had suffered dislocated shoulders were randomly assigned to one of two exercise programs. Those who engaged in static stretching returned to sports activity in a mean of 55.8 days (with a standard deviation of 29.4 days).Those assigned to the second program returned to sports in a mean
A pet supply company wants to compare a new lowercalorie food with their standard horse food to see if it’s effective in helping inactive horses lower blood pressure.They have found several horse owners willing to participate in the trial. The horses have been classified as small, medium, or
Some people claim they can get relief from migraine headache pain by drinking a large glass of ice water. Researchers plan to enlist several people who suffer from migraines in a test. When a participant experiences a migraine headache, he or she will take a pill that may be a standard pain
Some people who race greyhounds give the dogs large doses of vitamin C in the belief that the dogs will run faster. Investigators at the University of Florida tried three different diets in random order on each of five racing greyhounds. They were surprised to find that when the dogs ate high
The May 4, 2000, issue of Science News reported that, contrary to popular belief, depressed individuals cry no more often in response to sad situations than nondepressed people. Researchers studied 23 men and 48 women with major depression and 9 men and 24 women with no depression. They showed the
Scientists at a major pharmaceutical firm investigated the effectiveness of an herbal compound to treat the common cold. They exposed each subject to a cold virus, then gave him or her either the herbal compound or a sugar solution known to have no effect on colds. Several days later, they assessed
In 2002, the journal Science reported that a study of women in Finland indicated that having sons shortened the life spans of mothers by about 34 weeks per son, but that daughters helped to lengthen the mothers’ lives. The data came from church records from the period 1640 to 1870. What’s the
Researchers have linked an increase in the incidence of breast cancer in Italy to dioxin released by an industrial accident in 1976. The study identified 981 women who lived near the site of the accident and were under age 40 at the time. Fifteen of the women had developed breast cancer at an
After menopause, some women take supplemental estrogen.There is some concern that if these women also drink alcohol, their estrogen levels will rise too high.Nineteen volunteers who were receiving supplemental estrogen were randomly divided into two groups, as were 20 other volunteers not on
Is diet or exercise effective in combating insomnia?Some believe that cutting out desserts can help alleviate the problem, while others recommend exercise. Forty volunteers suffering from insomnia agreed to participate in a month-long test. Half were randomly assigned to a special no-desserts diet;
In a test of 1000 children, those with high blood pressure did worse on tests of memory and reaction time than those with normal blood pressure. What’s the design? Read each brief report of statistical research, and identifya) whether it was an observational study or an experiment.If it was an
Among a group of disabled women aged 65 and older who were tracked for several years, those who had a vitamin B12 deficiency were twice as likely to suffer severe depression as those who did not. (Source: American Journal of Psychiatry 157 [2000]: 715) What’s the design? Read each brief report of
Over a 4-month period, among 40 people with bipolar disorder, patients who were given a high dose (775 mg>day) of a certain dietary supplement improved more than those given a placebo. What’s the design? Read each brief report of statistical research, and identifya) whether it was an
Honesty Coffee stations in offices often just ask users to leave money in a tray to pay for their coffee, but many people cheat. Researchers at Newcastle University replaced the picture of flowers on the wall behind the coffee station with a picture of staring eyes. They found that the average
Menopause Researchers studied the herb black cohosh as a treatment for hot flashes caused by menopause. They randomly assigned 318 women aged 55 to 60 who reported at least two hot flashes a day to one of five groups:(1) black cohosh, (2) a multiherb supplement with black cohosh, (3) the multiherb
Super Bowl commercials When spending large amounts to purchase advertising time, companies want to know what audience they’ll reach. In January 2011, a poll asked 1008 American adults whether they planned to watch the upcoming Super Bowl. Men and women were asked separately whether they were
MS and vitamin D Multiple sclerosis (MS) is an autoimmune disease that strikes more often the farther people live from the equator. Could vitamin D—which most people get from the sun’s ultraviolet rays—be a factor? Researchers compared vitamin D levels in blood samples from 150 U.S.military
Heart attacks and height Researchers who examined health records of thousands of males found that men who died of myocardial infarction (heart attack) tended to be shorter than men who did not.a) Is this an experiment? If not, what kind of study is it?b) Is it correct to conclude that shorter men
Standardized test scores For his Statistics class experiment, researcher J. Gilbert decided to study how parents’income affects children’s performance on standardized tests like the SAT. He proposed to collect information from a random sample of test takers and examine the relationship between
Tomatoes finis What factors might confound the results of the experiment in Exercise 4?
Confounded tips For the experiment of Exercise 3, name some confounding variables that might influence the experiment’s results?
Blocking tomatoes To obtain enough plants for the tomato experiment of Exercise 4, experimenters have to purchase plants from two different garden centers.They then randomly assign the plants from each garden center to all three fertilizer treatments. Is the experiment blocked? Is that a good idea?
Block that tip The driver of Exercise 3 wants to know about tipping in general. So he recruits several other drivers to participate in the experiment. Each driver randomly decides whether to phone customers before delivery and records the tip percentage. Is this experiment blocked? Is that a good
More tomatoes If the tomato taster doesn’t know how the tomatoes have been treated, is the experiment single or double-blind? How might the blinding be improved further?
More tips Is the experiment of Exercise 3 blinded? Can it be double-blinded? Explain.
Tomatoes again For the experiment of Exercise 4, discuss variables that could be controlled or that could not be controlled. Is the experiment randomized and replicated?
Tips again For the experiment of Exercise 3, name some variables the driver did or should have controlled. Was the experiment randomized and replicated?
Tomatoes II For the experiment described in Exercise 4, name the factor and its levels. How might the response be measured?
Tips II For the experiment described in Exercise 3, list the factor, the levels, and the response variable.
Tomatoes You want to compare the tastiness and juiciness of tomatoes grown with three amounts of a new fertilizer: none, half the recommended amount, and the full recommended amount. You allocate 6 tomato plants to receive each amount of fertilizer, assigning them at random. What are the
Tips A pizza delivery driver, always trying to increase tips, runs an experiment on his next 40 deliveries. He flips a coin to decide whether or not to call a customer from his mobile phone when he is five minutes away, hoping this slight bump in customer service will lead to a slight bump in tips.
E-commerce A business student conjectures that the Internet caused companies to become more profitable, since many transactions previously handled “face-to-face”could now be completed online. The student compares earnings from a sample of companies from the 1980s to a sample from the 2000s.
Steroids The 1990s and early 2000s could be considered the steroids era in Major League Baseball, as many players have admitted to using the drug to increase performance on the field. If a sports writer wanted to compare home run totals from the steroids era to an earlier decade, say the 1960s,
After many dogs and cats suffered health problems caused by contaminated foods, we’re trying to find out whether a newly formulated pet food is safe. Our experiment will feed some animals the new food and others a food known to be safe, and a veterinarian will check the response.Question: Why
In our experiment to see if the new pet food is now safe, we’re feeding one group of dogs the new food and another group a food we know to be safe. Our response variable is the health of the animals as assessed by a veterinarian.Questions: Should the vet be blinded? Why or why not? How would you
We’re planning an experiment to see whether the new pet food is safe for dogs to eat. We’ll feed some animals the new food and others a food known to be safe, comparing their health after a period of time.Question: In this experiment, how will you implement the principles of control,
Recap: In 2007, deaths of a large number of pet dogs and cats were ultimately traced to contamination of some brands of pet food. The manufacturer now claims that the food is safe, but before it can be released, it must be tested.Question: In an experiment to test whether the food is now safe for
In early 2007, a larger-than-usual number of cats and dogs developed kidney failure;many died. Initially, researchers didn’t know why, so they used an observational study to investigate.Question: Suppose you were called on to plan a study seeking the cause of this problem. Would your design be
More sampling methods Consider each of these situations.Do you think the proposed sampling method is appropriate?Explain.a) We want to know if there is neighborhood support to turn a vacant lot into a playground. We spend a Saturday afternoon going door-to-door in the neighborhood, asking people to
Sampling methods Consider each of these situations. Do you think the proposed sampling method is appropriate?Explain.a) We want to know what percentage of local doctors accept Medicaid patients. We call the offices of 50 doctors randomly selected from local Yellow Pages listings.b) We want to know
A fish story Concerned about reports of discolored scales on fish caught downstream from a newly sited chemical plant, scientists set up a field station in a shoreline public park. For one week, they asked fishermen there to bring any fish they caught to the field station for a brief inspection. At
Quality control Sammy’s Salsa, a small local company, produces 15 cases of salsa a day. Each case contains 12 jars and is imprinted with a code indicating the date and batch number. To help maintain consistency, at the end of each day, Sammy selects two jars of salsa, weighs the contents, and
Happy workers? A manufacturing company employs 14 project managers, 48 supervisors, and 377 laborers. In an effort to keep informed about any possible sources of employee discontent, management wants to conduct job satisfaction interviews with a sample of employees every month.a) Do you see any
Accounting Between quarterly audits, a company likes to check on its accounting procedures to address any problems before they become serious. The accounting staff processes payments on about 120 orders each day.The next day, the supervisor rechecks 10 of the transactions to be sure they were
Fuel economy Occasionally, when I fill my car with gas, I figure out how many miles per gallon my car got.I wrote down those results after five fill-ups in the past few months. Overall, it appears my car gets 22.6 miles per gallon.a) What statistic have I calculated?b) What is the parameter I’m
Arm length How long is your arm compared with your hand size? Put your right thumb at your left shoulder bone, stretch your hand open wide, and extend your hand down your arm. Put your thumb at the place where your little finger is, and extend down the arm again. Repeat this a third time. Now your
Cell phone survey What about drawing a random sample only from cell phone exchanges? Discuss the advantages and disadvantages of such a sampling method compared with surveying randomly generated telephone numbers from non–cell phone exchanges. Do you think these advantages and disadvantages have
Phone surveys Any time we conduct a survey, we must take care to avoid undercoverage. Suppose we plan to select 500 names from the city phone book, call their homes between noon and 4 p.m., and interview whoever answers, anticipating contacts with at least 200 people.a) Why is it difficult to use a
More survey questions Examine each of the following questions for possible bias. If you think the question is biased, indicate how and propose a better question.a) Do you think high school students should be required to wear uniforms?b) Given humanity’s great tradition of exploration, do you
Survey questions Examine each of the following questions for possible bias. If you think the question is biased, indicate how and propose a better question.a) Should companies that donate to the Koala Bear Foundation be compelled to pay the costs to restore the rainforest?b) Given that 16-year-olds
Banning ephedra An online poll on a website asked:A nationwide ban of the diet supplement ephedra went into effect recently. The herbal stimulant has been linked to 155 deaths and many more heart attacks and strokes.Ephedra manufacturer NVE Pharmaceuticals, claiming that the FDA lacked proof that
Wording the survey Two members of the PTA committee in Exercises 26 and 27 have proposed different questions to ask in seeking parents’ opinions.Question 1: Should elementary school–age children have to pass high-stakes tests in order to remain with their classmates?Question 2: Should schools
Playground, act two The survey described in Exercise 29 asked: Many people believe this playground is too small and in need of repair. Do you think the playground should be repaired and expanded even if that means raising the entrance fee to the park?Describe two ways this question may lead to
Roller coasters An amusement park has opened a new roller coaster. It is so popular that people are waiting for up to 3 hours for a 2-minute ride. Concerned about how patrons (who paid a large amount to enter the park and ride on the rides) feel about this, they survey the first 100 people as they
Playground Some people have been complaining that the children’s playground at a municipal park is too small and is in need of repair. Managers of the park decide to survey city residents to see if they believe the playground should be rebuilt. They hand out questionnaires to parents who bring
Churches For your political science class, you’d like to take a survey from a sample of all the Mormon Church members in your city. A list of places of worship shows 24 Mormon temples within the city limits. Rather than try to obtain a list of all members of all these temples, you decide to pick
Parent opinion, part 2 Let’s revisit the school system described in Exercise 26. Four new sampling strategies have been proposed to help the PTA determine whether parents favor requiring elementary students to pass a test in order to be promoted to the next grade. For each, indicate what kind of
Parent opinion, part 1 In a large city school system with 20 elementary schools, the school board is considering the adoption of a new policy that would require elementary students to pass a test in order to be promoted to the next grade. The PTA wants to find out whether parents agree with this
Another mistaken poll Prior to the mayoral election discussed in Exercise 24, the newspaper also conducted a poll. The paper surveyed a random sample of registered voters stratified by political party, age, sex, and area of residence. This poll predicted that Amabo would win the election with 52%
Mistaken poll A local TV station conducted a “Pulse-Poll” about the upcoming mayoral election. Evening news viewers were invited to text in their votes, with the results to be announced on the late-night news. Based on the texts, the station predicted that Amabo would win the election with 52%
Egg samples Food-safety inspectors visit poultry farms unannounced and take samples of a day’s worth of eggs to test for contamination. If the samples are found to contain dirt, antibiotics, or other foreign matter, the eggs will be destroyed and the farm reinspected until purity is restored.
Pretzels A company packaging pretzels maintains quality control by randomly selecting 15 cases from each day’s production and weighing the bags. Then they open one bag from each case and inspect the contents.
Roadblock State police set up a roadblock to estimate the percentage of cars with up-to-date registration, insurance, and safety inspection stickers. They usually find problems with about 10% of the cars they stop.
Global warming A magazine interviewed 1047 randomly selected people. The magazine reports that when asked when (if ever) the effects of global warming will begin to happen, 65% of respondents said the effects had already begun. Only 12% thought they would never happen.
Mayoral race Hoping to learn what issues may resonate with voters in the coming election, the campaign director for a mayoral candidate selects one block from each of the city’s election districts. Staff members go there and interview all the adult residents they can find.
Social life A question posted on the gamefaqs.com website on August 1, 2011, asked visitors to the site, “Do you have an active social life outside the Internet?” 22% of the 55,581 respondents said “No” or “Not really, most of my personal contact is online.”
Medical treatments A consumer magazine asked all subscribers whether they had used alternative medical treatments and, if so, whether they had benefited from them. For almost all of the treatments, approximately 16% of those responding reported cures or substantial improvement in their condition.
Gallup At its website (www.gallup.com), the Gallup Poll publishes results of a new survey each day. Scroll down to the end, and you’ll find a statement that includes words such as these:Results are based on telephone interviews with 1016 national adults, aged 18 and older, conducted March 7–10,
Drug tests Major League Baseball tests players to see whether they are using performance-enhancing drugs.Officials select a team at random, and a drug-testing crew shows up unannounced to test all 40 players on the team.Each testing day can be considered a study of drug use in Major League
Student center survey For their class project, a group of Statistics students decide to survey the student body to assess opinions about the proposed new student center. Their sample of 180 contained 45 first-year students, 45 sophomores, 45 juniors, and 45 seniors.a) Do you think the group was
Roper Through their Roper Reports Worldwide, GfK Roper conducts a global consumer survey to help multinational companies understand different consumer attitudes throughout the world. Within 30 countries, the researchers interview 1000 people aged 13–65. Their samples are designed so that they get
Surveying employees The company of Exercise 2 is considering ways to survey their employees. For each of these proposed designs, identify the problem.a) Leave a stack of surveys out in the employee cafeteria so people can pick them up and return them.b) Stuff a questionnaire in the mailbox of each
Student samples The university administration of Exercise 1 is considering a variety of ways to sample students for a survey. For each of these proposed survey designs, identify the problem.a) Publish an advertisement inviting students to visit a website and answer questions.b) Set up a table in
Happy employees The company plans to have the head of each corporate division hold a meeting of their employees to ask whether they are happy on their jobs. They will ask people to raise their hands to indicate whether they are happy. What problems do you see with this plan?
Survey students What problems do you see with asking the following question of students? “Are you the first member of your family to seek higher education?”
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