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Statistics Concepts And Controversies 7th Edition David S Moore, William I Notz - Solutions

Seat belt safety. The National Highway Traffic Safety Administration reports that in 2006, between the hours of 6 A.M. and 6 P.M., 8160 occupants of motor vehicles who were wearing a restraint died in motor vehicle accidents and 7064 who were not wearing a restraint died. These numbers suggest that
Measuring physical fitness. You want to measure the “physical fitness”of college students. Give an example of a clearly invalid way to measure fitness.Then briefly describe a measurement process that you think is valid.AppendixLO1
Counting the unemployed? We could measure the extent of unemployment by a count (the number of people who are unemployed) or by giving a rate (the percentage of the labor force that is unemployed). The number of people in the labor force grew from 107 million in 1980, to 126 million in 1990, to 143
The most popular restaurant. Each year the Zagat Survey lists the most popular restaurants in Los Angeles. In 2005, A.O.C. was ranked 5th but in 2004 it was ranked 31st. The Cheesecake Factory was ranked 7th in 2005 but was 2nd in 2004. Are these ratings biased or unreliable?AppendixLO1
Driver fatigue. A researcher studied the number of traffic accidents that were attributed to driver fatigue at different times of the day. He noticed that the number of accidents was higher in the late afternoon (between 5 and 6 P.M.) than in the early afternoon (between 1 and 2 P.M.). He concluded
Web-based exercise. To see how software speeds up choosing an SRS, go to the Research Randomizer at www.randomizer.org. Click on“Randomize Now” and fill in the boxes. You can even ask the Randomizer to arrange your sample in order.
Web-based exercise. There are several voluntary response polls available on the Internet. Visit www.misterpoll.com and examine several of the current polls. What are the sample sizes in these polls? Who can vote? Is it possible to vote more than once? Do you think you can trust the results of the
Random selection? Choosing at random is a “fair” way to decide who gets some scarce good, in the sense that everyone has the same chance to win.Random choice isn’t always a good idea—sometimes we don’t want to treat everyone the same, because some people have a better claim. In each of
Racial profiling and traffic stops. The Denver Police Department wants to know if Hispanic residents of Denver believe that the police use racial profiling when making traffic stops. A sociologist prepares several questions about the police. The police department chooses an SRS of 200 mailing
More randomization. Most sample surveys call residential telephone numbers at random. They do not, however, always ask their questions of the person who picks up the phone. Instead, they ask about the adults who live in the residence and choose one at random to be in the sample. Why is this a good
Tuition for illegal immigrants. As part of a project for a political science class, a student decided to conduct an online poll asking the following question: “Do you think that illegal immigrants should be allowed to pay instate tuition, even though they are not legal citizens of that state?”
How do random digits behave? Which of the following statements are true of a table of random digits, and which are false? Explain your answers.(a) Each pair of digits has chance 1/100 of being 33.(b) There are exactly four 4s in each row of 40 digits.(c) The digits 99999 can never appear as a
Apartment living. You are planning a report on apartment living in a college town. You decide to select three apartment complexes at random for indepth interviews with residents. Use Table A, starting at line 117, to select a Chapter 2 Exercises 33 simple random sample of three of the following
How much do students pay for rent? A university’s housing and residence office wants to know how much students pay per month for rent in offcampus housing. The university does not have enough on-campus housing for students and this information will be used in a brochure about student housing.The
Is this an SRS? A university has 30,000 undergraduate and 10,000 graduate students. A survey of student opinion concerning health care benefits for domestic partners of students selects 300 of the 30,000 undergraduate students at random and then separately selects 100 of the 10,000 graduate
An election day sample. You want to choose an SRS of 20 of a city’s 480 voting precincts for special voting-fraud surveillance on election day.(a) Explain clearly how you would label the 480 precincts. How many digits make up each of your labels? What is the greatest number of precincts you could
Choose an SRS. Your class in ancient Ugaritic religion is poorly taught and the class members have decided to complain to the dean. The class decides to choose 4 of its members at random to carry the complaint. The class list appears below. Choose an SRS of 4 using the table of random digits,
Choose an SRS. A firm wants to understand the attitudes of its minority managers toward its system for assessing management performance. Below is a list of all the firm’s managers who are members of minority groups. Use Table A at line 137 to choose 6 to be interviewed in detail about the
Call-in versus random sample polls. A national survey of TV network news viewers found that 48% said they would believe a phone-in poll of 300,000 persons rather than a random sample of 1000 persons. Of the viewers, 42% said they would believe the random sample poll. Explain to someone who knows no
A call-in opinion poll. In 2005 the San Francisco Bay Times reported on a poll in New Zealand that found that New Zealanders opposed the nation’s new gay-inclusive civil-unions law by a 3-1 ratio.This poll was a call-in poll that cost $1 to participate in. The San Francisco Bay Times article also
Design your own bad sample. Your college wants to gather student opinion about parking for students on campus. It isn’t practical to contact all students.(a) Give an example of a way to choose a sample of students that is poor practice because it depends on voluntary response.(b) Give an example
We don’t like one-way streets. Highway planners decided to make a main street inWest Lafayette, Indiana, a one-way street. The Lafayette Journal Chapter 2 Exercises 31 and Courier took a one-day poll by inviting readers to call a telephone number to record their comments. The next day, the paper
Ann Landers takes a sample. Advice columnist Ann Landers once asked her divorced readers whether they regretted their decision to divorce. She received approximately 30,000 responses, about 23,000 of which came from women. Nearly 75% said they were glad they divorced, and most of them said they
Instant opinion. The BusinessWeek online poll can be found at the Web site indicated in the “Notes and Data Sources,” on page 34. The latest question appears on the screen, and visitors to the site can simply click buttons to vote.On March 29, 2007, the question was “Do you think Google is
Letters to the editor. You work for a local newspaper that has recently reported on a bill that would make it easier to create charter schools in the state. You report to the editor that 201 letters have been received on the issue, of which 171 oppose the legislation. “I’m surprised that most
Evaluating teaching assistants. To assess how its teaching assistants are performing, the statistics department at a large university randomly selects 3 of its teaching assistants each week and sends a faculty member to visit their classes. The current list of 20 teaching assistants is given below.
Sampling my class. There are 20 students in my class.They sit in assigned seats, consisting of four rows of five students each. I want to take a simple random sample consisting of 4 of the students in my class. To do this I select a single student from each row as follows. I write the numbers 1 to
Web-based exercise. The Statistical Abstract of the United States is an essential compilation of data. You can find it online at the Census Bureau Web site. The most recent edition is at www.census.gov/compendia/statab/. To find what you want, you can use the search tool at the Web site. Use the
Web-based exercise. In Exercise 9.14 you were asked to compute the percentage drop in the Dow Jones Industrial Average on September 17, 2001. Because the index had gone up so much in previous years, this was not the biggest percentage drop ever. Go to
Web-based exercise. Find an example of one of the following. Explain in detail the statistical shortcomings of your example.Leaving out essential information Lack of consistency Implausible numbers Faulty arithmetic One place to look is in the online Chance News. The CHANCE Web site at Dartmouth
Time off. The pointy-haired boss in the Dilbert cartoon once noted that 40% of all sick days taken by the staff are Fridays and Mondays. Is this evidence that the staff are trying to take long weekends?EXPLORING THE WEB
Boating safety. Data on accidents in recreational boating in the Statistical Abstract of the United States show that the number of deaths has dropped from 1360 in 1980 to 676 in 2004. However, the number of injuries reported grew from 2650 in 1980 to 3363 in 2004. Why are there so few deaths in
Being on top also matters. The previous exercise noted that median family income decreased slightly between 2002 and 2004. The top 5% of Chapter 9 Exercises 179 households earned $172,605 or more in 2002 and $173,640 or more in 2004.(These amounts are in dollars of 2004 buying power.) By what
Where you start matters. When comparing numbers over time, you can slant the comparison by choosing your starting point. Say the Chicago Cubs lose 5 games, then win 4, then lose 1. You can truthfully say that the Cubs have lost 6 of their last 10 games (sounds bad) or that they have won 4 of their
Too good to be true? The late English psychologist Cyril Burt was known for his studies of the IQ scores of identical twins who were raised apart.The high correlation between the IQs of separated twins in Burt’s studies pointed to heredity as a major factor in IQ. (“Correlation” measures how
No eligible men? A news report quotes a sociologist as saying that for every 233 unmarried women in their 40s in the United States, there are only 100 unmarried men in their 40s. These numbers point to an unpleasant social situation for women of that age. Are the numbers plausible? (Optional: The
In the garden. Organic Gardening magazine, describing how to improve your garden’s soil, said, “Since a 6-inch layer of soil in a 100-square-foot plot weighs about 45,000 pounds, adding 230 pounds of compost will give you an instant 5% organic matter.”(a) What percent of 45,000 is
How many miles of highways? Organic Gardening magazine once said that “the U.S. Interstate Highway System spans 3.9 million miles and is wearing out 50% faster than it can be fixed. Continuous road deterioration adds$7 billion yearly in fuel costs to motorists.” The distance from the east coast
Don’t dare to drive? A university sends a monthly newsletter on health to its employees. One issue included a column called “What Is the Chance?” that said:Chance that you’ll die in a car accident this year: 1 in 75.There are about 304 million people in the United States. About 42,000
Greeks on campus. The question-and-answer column of a campus newspaper was asked what percentage of the campus was “Greek” (that is, members of fraternities or sororities). The answer given was that “the figures for the fall semester are approximately 12 percent for the girls and 15–18
Rinse your mouth. A new mouth rinse claimed to “reduce plaque on teeth by 300%.” Explain carefully why it is impossible to reduce anything by 300%.
We don’t lose your baggage. Continental Airlines once advertised that it had “decreased lost baggage by 100% in the past six months.” Do you believe this claim?
Poverty. The number of Americans living below the official poverty line increased from 24,975,000 to 36,950,000 in the 30 years between 1976 and 2005. What percentage increase was this? You should not conclude from this that poverty grew more common in these years, however. Why not?
Stocks go down. On September 17, 2001, the Dow Jones Industrial Average dropped 685 points from its opening level of 9605. This was the biggest one-day decline ever and occurred on the first day the New York Stock Exchange was open following the attacks on September 11, 2001. By what percentage did
We can read, but can we count? The Census Bureau once gave a simple test of literacy in English to a random sample of 3400 people. The New York Times printed some of the questions under the headline “113% of Adults in U.S. Failed This Test.” Why is the percent in the headline clearly wrong?
Battered women? A letter to the editor of the New York Times complained about a Times editorial that said “an American woman is beaten by her husband or boyfriend every 15 seconds.” The writer of the letter claimed that “at that rate, 21 million women would be beaten by their husbands or
How many miles do we drive? Here is an excerpt from Robert Sullivan’s “A Slow-Road Movement?” in the Sunday magazine section of the New York Times on June 25, 2006:According to the Automobile Association of America, in 1956, Americans drove 628 million miles; in 2002, 2.8 billion. The even
Airport delays. An article in a midwestern newspaper about flight delays at major airports said:According to a Gannett News Service study of U.S. airlines’performance during the past five months, Chicago’s O’Hare Field scheduled 114,370 flights. Nearly 10 percent, 1,136, were canceled.Check
Funny numbers. Here’s a quotation from a book review in a scientific journal:. . .a set of 20 studies with 57 percent reporting significant results, of which 42 percent agree on one conclusion while the remaining 15 percent favor another conclusion, often the opposite one.Do the numbers given in
Trash at sea? A report on the problem of vacation cruise ships polluting the sea by dumping garbage overboard said:On a seven-day cruise, a medium-size ship (about 1,000 passengers) might accumulate 222,000 coffee cups, 72,000 soda cans, 40,000 beer cans and bottles, and 11,000 wine bottles.Are
Suicides among Vietnam veterans. Did the horrors of fighting in Vietnam drive many veterans of that war to suicide? A figure of 150,000 suicides among Vietnam veterans in the 20 years following the end of the war has been widely quoted. Explain why this number is not plausible. To help you, here
Deer in the suburbs. Westchester County is a suburban area covering 438 square miles immediately north of New York City. A garden magazine claimed that the county is home to 800,000 deer. Do a calculation that shows this claim to be implausible.
Advertising painkillers. Anacin was long advertised as containing “more of the ingredient doctors recommend most.” Another over-the-counter pain reliever claimed that “doctors specify Bufferin most” over other “leading brands.”Both advertising claims were literally true; the Federal
Advertising painkillers. An advertisement for the pain reliever Tylenol was headlined “Why Doctors Recommend Tylenol More Than All Leading Aspirin Brands Combined.” The makers of Bayer Aspirin, in a reply headlined“Makers of Tylenol, Shame on You!” accused Tylenol of misleading by giving
Drunk driving. A newspaper article on drunk driving cited data on traffic deaths in Rhode Island: “Forty-two percent of all fatalities occurred on Friday, Saturday, and Sunday, apparently because of increased drinking on the weekends.” What percent of the week do Friday, Saturday, and Sunday
Percentage increase and decrease. On the first quiz of the term (worth 20 points total), a student scored a 5. On the second quiz, he scored a 10. Verify that the percentage increase from the first to the second quiz is 100%. On the third quiz, the student again scored Is there a hidden agenda? 173
Bombarded by Baptists? In a May 8, 1976, article, the New York Times reported, “Altogether, in some 30 associations and groups of independents, there are almost 80 million Baptists in the nation. They are outnumbered only by the Roman Catholics.” Is the number 80 million plausible? Visit the
Web-based exercise. You can find a (very) skeptical look at health claims not backed by proper clinical trials at the “Quackwatch” site, www.quackwatch.org. Visit the site and prepare a one-paragraph summary of one of the articles.AppendixLO1
Web-based exercise. Not all researchers agree that placebos have a powerful clinical effect. Go to the New England Journal of Medicine Web site (http://content.nejm.org) and find the article “Is the Placebo Powerless?An Analysis of Clinical Trials Comparing Placebo with No Treatment”by
Doctors and nurses. Nurse practitioners are nurses with advanced qualifications who often act much like primary care physicians. An experiment assigned 1316 patients who had no regular source of medical care to either a doctor (510 patients) or a nurse practitioner (806 patients). All of the
What do you want to know? The previous two exercises illustrate the use of statistically designed experiments to answer questions that arise in everyday life. Select a question of interest to you that an experiment might answer and briefly discuss the design of an appropriate experiment.AppendixLO1
Pizza Hut versus Domino’s. Do consumers prefer the taste of a pepperoni pizza from Pizza Hut or from Domino’s in a blind test in which neither slice of pizza is identified? Describe briefly the design of a matched pairs experiment to investigate this question.AppendixLO1
Speeding the mail? Is the number of days a letter takes to reach another city affected by the time of day it is mailed and whether the standard 5-digit zip code or the more informative 9-digit zip code is used? Describe briefly the design of an experiment with two explanatory variables to
In the cornfield. An agronomist (a specialist in crop production and soil chemistry) wants to compare the yield of 4 corn varieties. The field in which the experiment will be carried out increases in fertility from north to south.The agronomist therefore divides the field into 20 plots of equal
Comparing weight-loss treatments. Twenty overweight females have agreed to participate in a study of the effectiveness of 4 weight-loss treatments:A, B, C, and D. The researcher first calculates how overweight each subject is by comparing the subject’s actual weight with her “ideal” weight.
Comparing cancer treatments. The progress of a type of cancer differs in women and men. A clinical experiment to compare four therapies for this cancer therefore treats sex as a blocking variable.(a) You have 500 male and 300 female patients who are willing to serve as subjects. Use a diagram to
Mozart and manual dexterity. A researcher is interested in the effect of music on the performance of tasks requiring manual dexterity. She chooses playing Symphony no. 41 (the Jupiter Symphony) by Mozart as background music and playing no background music as treatments. The response variable is the
Does charting help investors? Some investors believe that charts of past trends in the prices of securities can help predict future prices. Most economists disagree. In an experiment to examine the effects of using charts, business students trade (hypothetically) a foreign currency at computer
Comparing hand strength. Is the right hand generally stronger than the left in right-handed people? You can crudely measure hand strength by placing a bathroom scale on a shelf with the end protruding, then squeezing the scale between the thumb below and the four fingers above. The reading of the
Peanut brittle. A food scientist wishes to study the effect of the type of pan and amount of sodium bicarbonate used in preparing peanut brittle on the flavor of the peanut brittle. In an experiment, peanut brittle is baked in four types of pans (iron, aluminum, stainless steel, and nonstick
Comparing corn varieties. New varieties of corn with altered amino acid content may have higher nutritional value than standard corn, which is low in the amino acid lysine. An experiment compares two new varieties, called opaque-2 and floury-2, with normal corn. The researchers mix corn-soybean
The best painkiller for children. A Washington Post article reported a study comparing the effectiveness of three common painkillers for children. Three hundred children, aged 6 to 17, were randomly assigned to three groups. Group A received a standard dose of ibuprofen.Group B received a standard
The placebo effect. A survey of physicians found that some doctors give a placebo to a patient who complains of pain for which the physician can find no cause. If the patient’s pain improves, these doctors conclude that it had no physical basis. The medical school researchers who conducted the
Testing a natural remedy. The statistical controversy presented in this chapter discusses issues surrounding the efficacy of natural remedies. The National Institutes of Health is at last sponsoring proper clinical trials of some natural remedies. In one study at Duke University, 330 patients with
Beating sunburn with broccoli. Some recent studies suggest that compounds in broccoli may be helpful in combating the effects of overexposure to ultraviolet radiation. Based on these studies we hope to show that a cream consisting of a broccoli extract reduces sunburn pain. Sixty patients suffering
Fatty acids and depression. A group of medical researchers studied the effects of the intake of omega-6 fatty acids relative to omega-3 fatty acids on depression. They randomly assigned 88 highly stressed and depressed subjects to either a diet high in omega-6 fatty acids relative to omega-3 fatty
Red wine and a long and happy life. A New York Times article reported that according to a study conducted by researchers at Harvard Medical School and the National Institute of Aging, a substance in red wine could extend life. In the study mice fed a high-fat diet and a large daily dose of
Daytime running lights. Canada requires that cars be equipped with“daytime running lights,” headlights that automatically come on at a low level when the car is started. Some manufacturers are now equipping cars sold in the United States with running lights. Will running lights reduce accidents
Treating acne. An article in a medical journal reports an experiment to see if pulsed dye laser therapy is effective in treating acne. The article describes the experiment as a “randomized, controlled, single-blinded split-face clinical trial of a volunteer sample of 40 patients aged 13 years or
Do hot peppers relieve pain? A researcher claims that the chemical capsaicin, the ingredient that makes chili peppers hot, helps relieve pain. He randomly assigns subjects with chronic back pain to two groups. In one group he injects capsaicin near the sciatic nerve. In the other he injects a
Magic mushrooms. A Washington Post article reported that psilocybin, the active ingredient of “magic mushrooms,” promoted a mystical experience in two-thirds of people who took it for the first time, according to a study published in the online journal Psychopharmacology.The authors of the
Low-carb versus low-fat. Researchers conducted an experiment to compare the effects of a carbohydrate-restricted diet (low-carb diet) and a calorie- and fat-restricted diet (low-fat diet) on weight loss. The researchers are concerned that the effect of diet may depend on gender, so sex is treated
Tasty cakes. A food company is preparing to market a new cake mix. It is important that the taste of the cake not be changed by small variations in baking time or temperature. In an 110 CHAPTER 6 Experiments in the Real World experiment, cakes made from the mix are baked at 300◦F, 320◦F, or
Web-based exercise. Go to the New England Journal of Medicine Web site (http://content.nejm.org) and find the article “Initial Treatment of Aggressive Lymphoma with High-Dose Chemotherapy and Autologous Stem-Cell Support” by Milpied et al. in the March 25, 2004, issue. Was this a comparative
Randomization at work. To demonstrate how randomization reduces confounding, consider the following situation. A nutrition experimenter intends to compare the weight gain of newly weaned male rats fed Diet A with that of rats fed Diet B. To do this, she will feed each diet to 10 rats. She has
Safety of anesthetics. The death rates of surgical patients differ for operations in which different anesthetics are used. An observational study found these death rates for four anesthetics:Anesthetic: Halothane Pentothal Cyclopropane Ether Death rate: 1.7% 1.7% 3.4% 1.9%This is not good evidence
Exercise and bone loss. Does regular exercise reduce bone loss in postmenopausal women? Here are two ways to study this question. Explain clearly why the second design will produce more trustworthy data.1. A researcher finds 1000 postmenopausal women who exercise regularly. She matches each with a
Prayer and meditation. You read in a magazine that “nonphysical treatments such as meditation and prayer have been shown to be effective in controlled scientific studies for such ailments as high blood pressure, insomnia, ulcers, and asthma.” Explain in simple language what the article means by
Treating prostate disease. A large study used records from Canada’s national health care system to compare the effectiveness of two ways to treat prostate disease. The two treatments are traditional surgery and a new method that does not require surgery. The records described many patients whose
Memantine and Alzheimer’s disease. Some medical researchers suspect that the drug memantine improves the cognition of patients with moderate to severe Alzheimer’s disease. You have available 50 people with moderate to severe Alzheimer’s disease who are willing to serve as subjects.98 CHAPTER
Statistical significance. A study, mandated by Congress when it passed No Child Left Behind in 2002, evaluated 15 reading and math software products used by 9424 students in 132 schools across the country during the 2004–2005 school year. It is the largest study that has compared students who
Statistical significance. A randomized comparative experiment examines whether the drug memantine improves the cognition of patients with moderate to severe Alzheimer’s disease. The subjects receive either memantine or a placebo for 24 weeks. The researchers conclude that on measures of
Treating drunk drivers. Once a person has been convicted of drunk driving, one purpose of court-mandated treatment or punishment is to prevent future offenses of the same kind. Suggest three different treatments that a court might require. Then outline the design of an experiment to compare their
Tool abrasion and sharpening angle. Use a diagram to describe a randomized comparative experimental design for the tool abrasion experiment of Exercise 5.14. Use Table A, starting at line 120, to do the randomization required by your design.AppendixLO1
Reducing health care spending. Will people spend less on health care if their health insurance requires them to pay some part of the cost themselves? An experiment on this issue asked if the percentage of medical costs that is paid by health insurance has an effect both on the amount of medical
Tool abrasion and sharpening angle. A manufacturer of chisels is interested in determining how the angle at which the cutting edge is sharpened affects tool abrasion. To answer this question, engineers obtain 20 similar chisels.They sharpen five chisels at each of 22.5, 25, 27.5, and 30 degrees.
Improving Chicago’s schools. The National Science Foundation(NSF) paid for “systemic initiatives” to help cities reform their public education systems in ways that should help students learn better.Does this program work? The initiative in Chicago focused on improving the teaching of
Conserving energy. Example 5 describes an experiment to learn whether providing households with electronic meters or with charts will reduce their electricity consumption. An executive of the electric company objects to including a control group. He says, “It would be cheaper to just compare
Do antioxidants prevent cancer? People who eat lots of fruits and vegetables have lower rates of colon cancer than those who eat little of these foods. Fruits and vegetables are rich in “antioxidants” such as vitamins A, C, and E. Will taking antioxidants help prevent colon cancer? A clinical
Learning on the Web. The discussion following Example 1 notes that the Nova Southeastern study does not tell us much aboutWeb versus classroom learning because the students who chose the Web version were much better prepared. Describe the design of an experiment to get better information.96 CHAPTER

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