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business statistics in practice
The Practice Of Statistics 5th Edition Daren S. Starnes, Josh Tabor - Solutions
Wording bias 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 all cell phones come with a warning label explaining the danger of using cell
Checking for bias 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 control?1. The government should confiscate our guns.2. We have the right to keep
The Web portal AOL places opinion poll questions next to many of its news stories. Simply click your response to join the sample. One of the questions in January 2008 was “Do you plan to diet this year?”More than 30,000 people responded, with 68% saying“Yes.” You can conclude that(a) about
To gather information about the validity of a new standardized test for tenth-grade students in a particular state, a random sample of 15 high schools was selected from the state. The new test was administered to every 10th-grade student in the selected high schools. What kind of sample is this?(a)
Your statistics class has 30 students. You want to call an SRS of 5 students from your class to ask where they use a computer for the online quizzes. You label the students 01, 02, . . . , 30. You enter the table of random digits at this line:14459 26056 31424 80371 65103 62253 22490 61181 Your SRS
Suppose that 35% of the registered 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 outcome of the next election. If they randomly select 350 Republicans, randomly select 400
A local news agency conducted a survey about unemployment by randomly dialing phone numbers until they had gathered responses from 1000 adults in their state. In the survey, 19% of those who responded said they were not currently employed. In reality, only 6%of the adults in the state were not
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 additional money to establish a national system of health insurance?” Only 39% of those responding
Sleep debt (3.2) A researcher reported that the typical teenager needs 9.3 hours of sleep per night but gets only 6.3 hours.18 By the end of a 5-day school week, a teenager would accumulate about 15 hours of “sleep debt.” Students in a high school statistics class were skeptical, so they
Internet charges (2.1) Some Internet service providers(ISPs) charge companies based on how much bandwidth they use in a month. One method that ISPs use for calculating bandwidth is to find the 95th percentile of a company’s usage based on samples of hundreds of 5-minute intervals during a
Distinguish between an observational study and an experiment.
Explain the concept of confounding and how it limits the ability to make cause-and-effect conclusions.
Identify the experimental units, explanatory and response variables, and treatments in an experiment.
Explain the purpose of comparison, random assignment, control, and replication in an experiment.
Describe a completely randomized design for an experiment, including how to randomly assign treatments using slips of paper, technology, or a table of random digits.
Describe the placebo effect and the purpose of blinding in an experiment.
Interpret the meaning of statistically significant in the context of an experiment.
Explain the purpose of blocking in an experiment.Describe a randomized block design or a matched pairs design for an experiment.
Does Taking Hormones Reduce Heart Attack Risk after Menopause?
Learning biology with computers 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 of a group of high school juniors, then randomly divides them into two groups. One group uses the
Cell phones and brain cancer One study of cell phones and the risk of brain cancer looked at a group of 469 people who have brain cancer. The investigators matched each cancer patient with a person of the same age, gender, and race who did not have brain cancer, then asked about the use of cell
Chocolate and happy babies A University of Helsinki(Finland) study wanted to determine if chocolate consumption during pregnancy had an effect on infant temperament at age 6 months. Researchers began by asking 305 healthy pregnant women to report their chocolate consumption. Six months after birth,
Child care and aggression 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 in child care from birth to age four-and-a-half, the more adults tended
Effects of class size Do smaller classes in elementary school really benefit students in areas such as scores on standardized tests, staying in school, and going on to college? We might do an observational study that compares students who happened to be in smaller and larger classes in their early
Effects of binge drinking A common definition of“binge drinking” is 5 or more drinks at one sitting for men and 4 or more for women. An observational study finds that students who binge drink have lower average GPA than those who don’t. Identify a variable that may be confounded with the
Growing in the shade Ability to grow in shade may help pines found in the dry forests of Arizona to resist drought. How well do these pines grow in shade? Investigators planted pine seedlings in a greenhouse in either full light, light reduced to 25% of normal by shade cloth, or light reduced to 5%
Internet telephone calls You can use Voice over Internet Protocol (VoIP) to make long-distance calls over the Internet. One of the most popular VoIP services is Skype. How will the appearance of ads during calls affect the use of this service? Researchers design an experiment to find out. They
Improving response rate How can we reduce the rate of refusals in telephone surveys? Most people who answer at all listen to the interviewer’s introductory remarks and then decide whether to continue. One study made telephone calls to randomly selected households to ask opinions about the next
Eat well and exercise Most American adolescents don’t eat well and don’t exercise enough. Can middle schools increase physical activity among their students? Can they persuade students to eat better? Investigators designed a “physical activity intervention”to increase activity in physical
Fabric science A maker of fabric for clothing is setting up a new line to “finish” the raw fabric. The line will use either metal rollers or natural-bristle rollers to raise the surface of the fabric; a dyeing-cycle time of either 30 or 40 minutes; and a temperature of either 150° or 175°C.
Exercise and heart rate A student project measured the increase in the heart rates of fellow students when they stepped up and down for 3 minutes to the beat of a metronome. The step was either 5.75 or 11.5 inches high and the metronome beat was 14, 21, or 28 steps per minute. Thirty students took
Cocoa and blood flow A study conducted by Norman Hollenberg, professor of medicine at Brigham and Women’s Hospital and Harvard Medical School, involved 27 healthy people aged 18 to 72. Each subject consumed a cocoa beverage containing 900 milligrams of flavonols (a class of flavonoids) daily for
Reducing unemployment Will cash bonuses speed the return to work of unemployed people? A state department of labor notes that last year 68% of people who filed claims for unemployment insurance found a new job within 15 weeks. As an experiment, this year the state offers $500 to people filing
Layoffs and “survivor guilt” Workers who survive a layoff of other employees at their location may suffer from “survivor guilt.” A study of survivor guilt and its effects used as subjects 120 students who were offered an opportunity to earn extra course credit by doing proofreading. Each
Effects of TV advertising Figure 4.2 (page 239) displays the 6 treatments for a two-factor experiment on TV advertising. Suppose we have 150 students who are willing to serve as subjects. Describe how you would randomly assign the subjects to the treatments(a) using slips of paper.(b) using
Stronger players A football coach hears that a new exercise program will increase upper-body strength better than lifting weights. He is eager to test this new program in the off-season with the players on his high school team. The coach decides to let his players choose which of the two treatments
Killing weeds A biologist would like to determine which of two brands of weed killer, X or Y, is less likely to harm the plants in a garden at the university.Before spraying near the plants, the biologist decides to conduct an experiment using 24 individual plants.Which of the following two plans
Do diets work? Dr. Linda Stern and her colleagues recruited 132 obese adults at the Philadelphia Veterans Affairs Medical Center in Pennsylvania.Half the participants were randomly assigned to a lowcarbohydrate diet and the other half to a low-fat diet.Researchers measured each participant’s
The effects of day care Does day care help low-income children stay in school and hold good jobs later in life? The Carolina Abecedarian Project (the name suggests the ABCs) has followed a group of 111 children since 1972. Back then, these individuals were all healthy but low-income black infants
Headache relief Doctors identify “chronic tensiontype headaches” as headaches that occur almost daily for at least six months. Can antidepressant medications or stress management training reduce the number and severity of these headaches? Are both together more effective than either alone?
More rain for California? The changing climate will probably bring more rain to California, but we don’t know whether the additional rain will come during the winter wet season or extend into the long dry season in spring and summer. Kenwyn Suttle of the University of California at Berkeley and
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
Getting teachers to come to school Elementary schools in rural India are usually small, with a single teacher. The teachers often fail to show up for work.Here is an idea for improving attendance: give the teacher a digital camera with a tamperproof time and date stamp and ask a student to take a
Do placebos really work? Researchers in Japan conducted an experiment on 13 individuals who were extremely allergic to poison ivy. On one arm, each subject was rubbed with a poison ivy leaf and told the leaf was harmless. On the other arm, each subject was rubbed with a harmless leaf and told it
Pain relief study Fizz Laboratories, a pharmaceutical company, has developed a new drug for relieving chronic pain. Sixty patients suffering from arthritis and needing pain relief are available. Each patient will be treated and asked an hour later, “About what percent of pain relief did you
Meditation for anxiety An experiment that claimed to show that meditation lowers anxiety proceeded as follows. The experimenter interviewed the subjects and rated their level of anxiety. Then the subjects were randomly assigned to two groups. The experimenter taught one group how to meditate and
Testosterone for older men As men age, their testosterone levels gradually decrease. This may cause a reduction in lean body mass, an increase in fat, and other undesirable changes. Do testosterone supplements reverse some of these effects? A study in the Netherlands assigned 237 men aged 60 to 80
Do diets work? Refer to Exercise 63. Subjects in the low-carb diet group lost significantly more weight than subjects in the low-fat diet group during the first six months. At the end of a year, however, the average weight loss for subjects in the two groups was not significantly different.42(a)
Acupuncture and pregnancy A study sought to determine whether the ancient Chinese art of acupuncture could help infertile women become pregnant.43 One hundred sixty healthy women undergoing assisted reproductive therapy were recruited for the study.Half of the subjects were randomly assigned to
Doctors and nurses Nurse-practitioners are nurses with advanced qualifications who often act much like primary-care physicians. Are they as effective as doctors at treating patients with chronic conditions?An experiment was conducted with 1316 patients who had been diagnosed with asthma, diabetes,
Comparing cancer treatments The progress of a type of cancer differs in women and men. Researchers want to design an experiment to compare three therapies for this cancer. They recruit 500 male and 300 female patients who are willing to serve as subjects.(a) Which are the blocks in this experiment:
In the cornfield An agriculture researcher wants to compare the yield of 5 corn varieties: A, B, C, D, and E. The field in which the experiment will be carried out increases in fertility from north to south. The researcher therefore divides the field into 25 plots of equal size, arranged in 5
Comparing weight-loss treatments Twenty overweight females have agreed to participate in a study of the effectiveness of four 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.
Aw, rats! 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 available 10 rats from one litter and 10 rats from a second litter. Rats in the first litter appear to be
Technology for teaching statistics The Brigham Young University (BYU) statistics department is performing experiments to compare teaching methods.Response variables include students’ final-exam scores and a measure of their attitude toward statistics.One study compares two levels of technology
Chocolate gets my heart pumping Cardiologists at Athens Medical School in Greece wanted to test whether chocolate affected blood flow in the blood vessels.The researchers recruited 17 healthy young volunteers, who were each given a 3.5-ounce bar of dark chocolate, either bittersweet or fake
Room temperature and dexterity An expert on worker performance is interested in the effect of room temperature on the performance of tasks requiring manual dexterity. She chooses temperatures of 70°F and 90°F as treatments. The response variable is the number of correct insertions, during a
Carbon dioxide and tree growth The concentration of carbon dioxide (CO2) in the atmosphere is increasing rapidly due to our use of fossil fuels. Because plants use CO2 to fuel photosynthesis, more CO2 may cause trees and other plants to grow faster. An elaborate apparatus allows researchers to pipe
Got deodorant? A group of students wants to perform an experiment to determine whether Brand A or Brand B deodorant lasts longer. One group member suggests the following design: Recruit 40 student volunteers—20 male and 20 female.Separate by gender, because male and female bodies might respond
Can changing diet reduce high blood pressure? Vegetarian diets and low-salt diets are both promising.Men with high blood pressure are assigned at random to four diets: (1) normal diet with unrestricted salt; (2) vegetarian with unrestricted salt; (3) normal with restricted salt; and (4) vegetarian
A farmer is conducting an experiment to determine which variety of apple tree, Fuji or Gala, will produce more fruit in his orchard. The orchard is divided into 20 equally sized square plots. He has 10 trees of each variety and randomly assigns each tree to a separate plot in the orchard. What are
Two essential features of all statistically designed experiments are(a) compare several treatments; use the double-blind method.(b) compare several treatments; use chance to assign subjects to treatments.(c) always have a placebo group; use the double-blind method.(d) use a block design; use chance
Seed weights (2.2) Biological measurements on the same species often follow a Normal distribution quite closely. The weights of seeds of a variety of winged bean are approximately Normal with mean 525 milligrams (mg) and standard deviation 110 mg.(a) What percent of seeds weigh more than 500
Twins (1.3, 3.1) A researcher studied a group of identical twins who had been separated and adopted at birth. In each case, one twin (Twin A) was adopted by a low-income family and the other (Twin B) by a high-income family. Both twins were given an IQ test as adults. Here are their scores:48 Twin
Describe the scope of inference that is appropriate in a statistical study.
Evaluate whether a statistical study has been carried out in an ethical manner.*
Does Smoking Cause Lung Cancer?
Random sampling versus random assignment Explain the difference between the types of inference that can be made as a result of random sampling and random assignment.
Observation versus experimentation Explain the difference between the types of inference than can usually be made from an observational study and an experiment.
Foster care versus orphanages Do abandoned children placed in foster homes do better than similar children placed in an institution? The Bucharest Early Intervention Project found that the answer is a clear “Yes.” The subjects were 136 young children abandoned at birth and living in orphanages
Frozen batteries Will storing batteries in a freezer make them last longer? To find out, a company that produces batteries takes a random sample of 100 AA batteries from its warehouse. The company statistician randomly assigns 50 batteries to be stored in the freezer and the other 50 to be stored
Who talks more—women or men? According to Louann Brizendine, author of The Female Brain, women say nearly three times as many words per day as men. Skeptical researchers devised a study to test this claim. They used electronic devices to record the talking patterns of 396 university students who
Attend church, live longer? One of the better studies of the effect of regular attendance at religious services gathered data from a random sample of 3617 adults.The researchers then measured lots of variables, not just the explanatory variable (religious activities) and the response variable
Daytime running lights Canada and the European Union require that cars be equipped with “daytime running lights,” headlights that automatically come on at a low level when the car is started. Many manufacturers are now equipping cars sold in the United States with running lights. Will running
Studying frustration A psychologist wants to study the effects of failure and frustration on the relationships among members of a work team. She forms a team of students, brings them to the psychology lab, and has them play a game that requires teamwork.The game is rigged so that they lose
Who reviews? Government regulations require that institutional review boards consist of at least five people, including at least one scientist, one nonscientist, and one person from outside the institution. Most boards are larger, but many contain just one outsider.(a) Why should review boards
No consent needed? In which of the circumstances below would you allow collecting personal information without the subjects’ consent?(a) A government agency takes a random sample of income tax returns to obtain information on the average income of people in different occupations.Only the incomes
Surveys of youth A survey asked teenagers whether they had ever consumed an alcoholic beverage.Those who said “Yes” were then asked, “How old were you when you first consumed an alcoholic beverage?”Should consent of parents be required to ask minors about alcohol, drugs, and other such
Anonymous? Confidential? One of the most important nongovernment surveys in the United States is the National Opinion Research Center’s General Social Survey. The GSS regularly monitors public opinion on a wide variety of political and social issues. Interviews are conducted in person in the
Anonymous? Confidential? Texas A&M, like many universities, offers screening for HIV, the virus that causes AIDS. Students may choose either anonymous or confidential screening. An announcement says,“Persons who sign up for screening will be assigned a number so that they do not have to give
The Willowbrook hepatitis studies In the 1960s, children entering the Willowbrook State School, an institution for the intellectually disabled on Staten Island in New York, were deliberately infected with hepatitis. The researchers argued that almost all children in the institution quickly became
Unequal benefits Researchers on aging proposed to investigate the effect of supplemental health services on the quality of life of older people. Eligible patients on the rolls of a large medical clinic were to be randomly assigned to treatment and control groups.The treatment group would be offered
Animal testing (1.1) “It is right to use animals for medical testing if it might save human lives.” The General Social Survey asked 1152 adults to react to this statement. Here is the two-way table of their responses:Male Female Strongly agree 76 59 Agree 270 247 Neither agree nor disagree 87
Initial public offerings (1.3) The business magazine Forbes reports that 4567 companies sold their first stock to the public between 1990 and 2000. The mean change in the stock price of these companies since the first stock was issued was +111%. The median change was −31%.58 Explain how this
Ontario Health Survey The Ministry of Health in the province of Ontario, Canada, wants to know whether the national health care system is achieving its goals in the province. Much information about health care comes from patient records, but that source doesn’t allow us to compare people who use
Bad sampling A large high school 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 voluntary response sample of students. Explain how this method could lead to bias.(b) Give an example of a way
Drug testing A baseball team regularly conducts random drug tests on its players. The 25 members of the team are listed below.Agarwal Chen Healy Moser Roberts Andrews Frank Hixson Musselman Shen Baer Fuest Lee Pavnica Smith Berger Fuhrmann Lynch Petrucelli Sundheim Brockman Garcia Milhalko Reda
Polling the faculty A researcher wants to study the attitudes of college faculty members about the work habits of entering freshmen. These attitudes appear to differ depending on the type of college.The American Association of University Professors classifies colleges as follows:Class I: Offer
Been to the movies? An opinion poll calls 2000 ran domly chosen residential telephone numbers, then asks to speak with an adult member of the household. The interviewer asks, “How many movies have you watched in a movie theater in the past 12 months?” In all, 1131 people responded. The
Are anesthetics safe? The National Halothane Study was a major investigation of the safety of anesthetics used in surgery. Records of over 850,000 operations performed in 34 major hospitals showed the following death rates for four common anesthetics:61 Anesthetic: A B C D Death rate: 1.7% 1.7%
fries. Potatoes are kept refrigerated before being cut for french fries to prevent spoiling and preserve flavor. But immediate processing of cold potatoes causes discoloring due to complex chemical reactions.The potatoes must therefore be brought to room temperature before processing. Researchers
Don’t catch a cold! A recent study of 1000 students at the University of Michigan investigated how to prevent catching the common cold. The students were randomly assigned to three different cold prevention methods for 6 weeks. Some wore masks, some wore masks and used hand sanitizer, and others
An herb for depression? Does the herb Saint-John’s-wort relieve major depression? Here is an excerpt from the report of a study of this issue:“Design: Randomized, Double-Blind, Placebo-Controlled Clinical Trial.”63 The study concluded that the difference in effectiveness of Saint-John’swort
How long did I work? A psychologist wants to know if the difficulty of a task influences our estimate of how long we spend working at it. She designs two sets of mazes that subjects can work through on a computer. One set has easy mazes and the other has difficult mazes. Subjects work until told to
Deceiving subjects Students sign up to be subjects in a psychology experiment. When they arrive, they are told that interviews are running late and are taken to a waiting room. The experimenters then stage a theft of a valuable object left in the waiting room. Some subjects are alone with the
When we take a census, we attempt to collect data from(a) a stratified random sample.(b) every individual chosen in a simple random sample.(c) every individual in the population.(d) a voluntary response sample.(e) a convenience sample.
You want to take a simple random sample (SRS) of 50 of the 816 students who live in a dormitory on campus. You label the students 001 to 816 in alphabetical order. In the table of random digits, you read the entries 95592 94007 69769 33547 72450 16632 81194 14873 The first three students in your
A study of treatments for angina (pain due to low blood supply to the heart) compared bypass surgery, angioplasty, and use of drugs. The study looked at the medical records of thousands of angina patients whose doctors had chosen one of these treatments. It found that the average survival time of
Tonya wanted to estimate the average amount of time that students at her school spend on Facebook each day. She gets an alphabetical roster of students in the school from the registrar’s office and numbers the students from 1 to 1137. Then Tonya uses a random number generator to pick 30 distinct
Consider an experiment to investigate the effectiveness of different insecticides in controlling pests and their impact on the productivity of tomato plants.What is the best reason for randomly assigning treatment levels (spraying or not spraying) to the experimental units (farms)?(a) Random
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