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Introduction To The Practice Of Statistics 6th Edition David S. Moore, George P. McCabe, Bruce A. Craig - Solutions

What type of study? What is the best way to answer each of the questions below: an experiment, a sample survey, or an observational study that is not a sample survey? Explain your choices.(a) Are people generally satisfied with how things are going in the country right now?(b) Do college students
Price promotions and consumers’expectations. A researcher studying the effect of price promotions on consumers’ expectations makes up two different histories of the store price of a hypothetical brand of laundry detergent for the past year. Students in a marketing course view one or the other
Prostate treatment study using Canada’s national health records. A large observational 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
Name the designs. What is the name for each of these study designs?(a) A study to compare two methods of preserving wood started with boards of southern white pine.Each board was ripped from end to end to form two edge-matched specimens. One was assigned to Method A; the other to Method B.(b) A
Cash bonuses for the unemployed. Will cash bonuses speed the return to work of unemployed people? The Illinois Department of Employment Security designed an experiment to find out. The subjects were 10,065 people aged 20 to 54 who were filing claims for unemployment insurance.Some were offered $500
Select a random sample of workers. The WORKERS data set contains information about 14,959 people aged 25 to 64 whose highest level of education is a bachelor’s degree.(a) In order to select an SRS of these people, how would you assign labels?(b) Use Table B at line 185 to choose the first 3
The 2000 census. The 2000 census long form asked 53 detailed questions, for example:Do you have COMPLETE plumbing facilities in this house, apartment, or mobile home; that is, 1) hot and and cold piped water, 2) a flush toilet, and 3) a bathtub or shower?The form also asked your income in dollars,
Should poll results be made public? Some people think that the law should require that all political poll results be made public. Otherwise, the possessors of poll results can use the information to their own advantage. They can act on the information, release only selected parts of it, or time the
Political polls. The presidential election campaign is in full swing, and the candidates have hired polling organizations to take regular polls to find out what the voters think about the issues. What information should the pollsters be required to give out?(a) What does the standard of informed
Testing vaccines. One of the most important goals of AIDS research is to find a vaccine that will protect against HIV. Because AIDS is so common in parts of Africa, that is the easiest place to test a vaccine. It is likely, however, that a vaccine would be so expensive that it could not (at least
Use of stored blood. Long ago, doctors drew a blood specimen from you as part of treating minor anemia. Unknown to you, the sample was stored.Now researchers plan to use stored samples from you and many other people to look for genetic factors that may influence anemia. It is no longer possible to
Anonymity and confidentiality in mail surveys. Some common practices may appear to offer anonymity while actually delivering only confidentiality. Market researchers often use mail surveys that do not ask the respondent’s identity but contain hidden codes on the questionnaire that identify the
Anonymity and confidentiality in health screening. Texas A&M, like many universities, offers free screening for HIV, the virus that causes AIDS. The announcement says, “Persons who sign up for the HIV Screening will be assigned a number so that they do not have to give their name.” They can
The General Social Survey. 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
Informed consent to take blood samples.Researchers from Yale, working with medical teams in Tanzania, wanted to know how common infection with the AIDS virus is among pregnant women in that country. To do this, they planned to test blood samples drawn from pregnant women.Yale’s institutional
Serving as an experimental subject for extra credit. Students taking Psychology 001 are required to serve as experimental subjects.Students in Psychology 002 are not required to serve, but they are given extra credit if they do so. Students in Psychology 003 are required either to sign up as
What is wrong? Explain what is wrong in each of the following scenarios.(a) Clinical trials are always ethical as long as they randomly assign patients to the treatments.(b) The job of an institutional review board is complete when they decide to allow a study to be conducted.(c) A treatment that
Should the treatments be given to everyone? Effective drugs for treating AIDS are very expensive, so most African nations cannot afford to give them to large numbers of people. Yet AIDS is more common in parts of Africa than anywhere else. Several clinical trials are looking at ways to prevent
Is this study ethical? 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
Should we allow this personal information to be collected? 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
How can we obtain informed consent? A researcher suspects that traditional religious beliefs tend to be associated with an authoritarian personality. She prepares a questionnaire that measures authoritarian tendencies and also asks many religious questions. Write a description of the purpose of
Who should be on an institutional review board? 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
Do these proposals involve minimal risk?Youareamember of your college’s institutional review board. You must decide whether several research proposals qualify for lighter review because they involve only minimal risk to subjects. Federal regulations say that “minimal risk”means the risks are
Toss a coin. Coin tossing can illustrate the idea of a sampling distribution. The population is all outcomes (heads or tails) we would get if we tossed a coin forever. The parameter p is the proportion of heads in this population. We suspect that p is close to 0.5. That is, we think the coin will
Simulate the sampling distribution of the mean.Continue the previous exercise, using software to illustrate the idea of a sampling distribution.(a) Choose 20 more SRSs of size 20 in addition to the 5 you have already chosen. Don’t make histograms of these latest samples—just record the mean GPA
Analyze simple random samples. The CSDATA data set contains the college grade point averages(GPAs) of all 224 students in a university entering class who planned to major in computer science.This is our population. Statistical software can take repeated samples to illustrate sampling
on the horizontal axis. Are your 10 sample values roughly centered at the population value? (If you kept going forever, your x-values would form the sampling distribution of the sample mean; the population mean would indeed be the center of this distribution.)
APPLET Use the simple random sample applet.The Simple Random Sample applet can illustrate the idea of a sampling distribution. Form a population labeled 1 to 100. We will choose an SRS of 10 of these numbers. That is, in this exercise, the numbers themselves are the population, not just labels for
Use Table B for a simulation. We can construct a sampling distribution by hand in the case of a very small sample from a very small population.The population contains 10 students. Here are their scores on an exam:Student 0 1 2 3 4 5 6 7 8 9 Score 82 62 80 58 72 73 65 66 74 62 The parameter of
CH ALLENGE Use the statistical software for simulations. Statistical software can speed simulations. We are interested in the sampling distribution of the proportion ˆp of people who find shopping frustrating in an SRS from a population in which proportion p find shopping frustrating.Here, p is a
APPLET Use the probability applet. The Probability applet simulates tossing a coin, with the advantage that you can choose the true long-term proportion, or probability, of a head. Example 3.33 discusses sampling from a population in which proportion p = 0.6 (the parameter) find shopping
The health care system in Ontario. The Ministry of Health in the Canadian province of Ontario wants to know whether the national health care system is achieving its goals in the province. The ministry conducted the Ontario Health Survey, which interviewed a probability sample of 61,239 adults who
Real estate ownership. An agency of the federal government plans to take an SRS of residents in each state to estimate the proportion of owners of real estate in each state’s population. The populations of the states range from less than 500,000 people in Wyoming to about 35 million in
Gallup Canada polls. Gallup Canada bases its polls of Canadian public opinion on telephone samples of about 1000 adults, the same sample size as Gallup uses in the United States. Canada’s population is about one-ninth as large as that of the United States, so the percent of adults that Gallup
Opinions of Hispanics. A New York Times News Service article on a poll concerned with the opinions of Hispanics includes this paragraph:The poll was conducted by telephone from July 13 to 27, with 3,092 adults nationwide, 1,074 of whom described themselves as Hispanic. It has a margin of sampling
Bias and variability. Figure 3.15 (on page 222)shows histograms of four sampling distributions of statistics intended to estimate the same parameter.Label each distribution relative to the others as high or low bias and as high or low variability.
Describe the population and the sample. For each of the following situations, describe the population and the sample.(a) A survey of 17,096 students in U.S. four-year colleges reported that 19.4% were binge drinkers.(b) In a study of work stress, 100 restaurant workers were asked about the impact
What’s wrong? State what is wrong in each of the following scenarios.(a) A sampling distribution describes the distribution of some characteristic in a population.(b) A statistic will have a large amount of bias whenever it has high variability.(c) The variability of a statistic based on a small
Effect of sample size on the sampling distribution. You are planning a study and are considering taking an SRS of either 200 or 400 observations. Explain how the sampling distribution would differ for these two scenarios.
Web polls. If you connect to theWeb site worldnetdaily.com/polls/, you will be given the opportunity to give your opinion about a different question of public interest each day. Can you apply the ideas about populations and samples that we have just discussed to this poll? Explain why or why not.
Sexual harassment of college students. A recent survey of 2036 undergraduate college students aged 18 to 24 reports that 62% of college students say they have encountered some type of sexual harassment while at college.43 Describe the sample and the population for this setting.
CHALLENGE Economic attitudes of Spaniards. Spain’s Centro de Investigaciones Sociol ´ ogicos carried out a sample survey on the economic attitudes of Spaniards.41 Of the 2496 adults interviewed, 72% agreed that “Employees with higher performance must get higher pay.” On the other hand, 71%
CHALLENGE Bad survey questions. Write your own examples of bad sample survey questions.(a) Write a biased question designed to get one answer rather than another.(b) Write a question that is confusing, so that it is hard to answer.
CHALLENGE How many children are in your family?A teacher asks her class, “How many children are there in your family, including yourself?” The mean response is about 3 children. According to the 2000 census, families that have children average 1.86 children. Why is a sample like this biased
Use of a budget surplus. In 2000, when the federal budget showed a large surplus, the Pew Research Center asked two questions of random samples of adults. Both questions stated that Social Security would be “fixed.” Here are the uses suggested for the remaining surplus:Should the money be used
Survey questions. 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
The Excite Poll. The Excite Poll can be found online at poll.excite.com. The question appears on the screen, and you simply click buttons to vote“Yes,” “No,” “Not sure,” or “Don’t care.” On July 22, 2006, the question was “Do you agree or disagree with proposed legislation that
The sampling frame. The list of individuals from which a sample is actually selected is called the sampling frame. Ideally, the frame should list every individual in the population, but in practice this is often difficult. A frame that leaves out part of the population is a common source of
Nonresponse in telephone surveys. A common form of nonresponse in telephone surveys is “ringno-answer.” That is, a call is made to an active number but no one answers. The Italian National Statistical Institute looked at nonresponse to a government survey of households in Italy during the
Stratified samples for accounting audits.Accountants use stratified samples during audits to verify a company’s records of such things as accounts receivable. The stratification is based on the dollar amount of the item and often includes 100% sampling of the largest items. One company reports
CH ALLENGE Stratified samples for alcohol attitudes.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 attitudes toward alcohol. You have given every student at the
Select club members to go to a convention. A club has 30 student members and 10 faculty members.The students are Abel Fisher Huber Moran Reinmann Carson Golomb Jimenez Moskowitz Santos Chen Griswold Jones Neyman Shaw David Hein Kiefer O’Brien Thompson Deming Hernandez Klotz Pearl Utts Elashoff
Stratified samples of forest areas. Stratified samples are widely used to study large areas of forest. Based on satellite images, a forest area in the Amazon basin is divided into 14 types. Foresters studied the four most commercially valuable types:alluvial climax forests of quality levels 1, 2,
Random digit telephone dialing. An opinion poll in California uses random digit dialing to choose telephone numbers at random. Numbers are selected separately within each California area code. The size of the sample in each area code is proportional to the population living there.(a) What is the
CHALLENGE Systematic random samples versus simple random samples. The previous exercise introduces systematic random samples. Explain carefully why a systematic random sample does give every individual the same chance to be chosen but is not a simple random sample.
Systematic random samples. Systematic random samples are often used to choose a sample of apartments in a large building or dwelling units in a block at the last stage of a multistage sample.An example will illustrate the idea of a systematic sample. Suppose that we must choose 4 addresses out of
A stratified sample. Exercise 3.61 asks you to choose an SRS of blocks from the census tract pictured in Figure 3.10. You might instead choose a stratified sample of one block from the 6 blocks in Group 1, two from the 12 blocks in Group 2, and three from the 26 blocks in Group 3. Choose such a
Repeated use of Table B. In using Table B repeatedly to choose samples or do randomization for experiments, you should not always begin at the same place, such as line 101. Why not?
Census tracts. The Census Bureau divides the entire country into “census tracts” that contain about 4000 people. Each tract is in turn divided into small “blocks,” which in urban areas are bounded by local streets. An SRS of blocks from a census tract is often the next-to-last stage in a
APPLET Use the simple random sample applet.There are approximately 371 active telephone area codes covering Canada, the United States, and some Caribbean areas. (More are created regularly.)You want to choose an SRS of 25 of these area codes for a study of available telephone numbers. Label the
APPLET Use the simple random sample applet.After you have labeled the individuals in a population, the Simple Random Sample applet automates the task of choosing an SRS. Use the applet to choose the sample in the previous exercise.
Using GIS to identify mint field conditions. A Geographic Information System (GIS) is to be used to distinguish different conditions in mint fields.Ground observations will be used to classifiy regions of each field as either healthy mint, diseased mint, or weed-infested mint. The GIS divides
Interview residents of apartment complexes.You are planning a report on apartment living in a college town. You decide to select 5 apartment complexes at random for in-depth interviews with residents. Select a simple random sample of 5 of the following apartment complexes. If you use Table B, start
Identify the populations. For each of the following sampling situations, identify the population as exactly as possible. That is, say what kind of individuals the population consists of and say exactly which individuals fall in the population. If the information given is not complete, complete the
Popularity of news personalities. A Gallup Poll conducted telephone interviews with 1001 U.S.adults aged 18 and over on July 24–27, 2006. One of the questions asked whether the respondents had a favorable or an unfavorable opinion of 17 news personalities. Diane Sawyer received the highest
Importance of students as customers. A committee on community relations in a college town plans to survey local businesses about the importance of students as customers. From telephone book listings, the committee chooses 150 businesses at random. Of these, 73 return the questionnaire mailed by the
What’s wrong? Explain what is wrong with each of the following random selection procedures and explain how you would do the randomization correctly.(a) To determine the reading level of an introductory statistics text, you evaluate all of the written material in the third chapter.(b) You want to
What’s wrong? Explain what is wrong in each of the following scenarios.(a) The population consists of all individuals selected in a simple random sample.(b) In a poll of an SRS of residents in a local community, respondents are asked to indicate the level of their concern about the dangers of
Listen to three songs. The walk to your statistics class takes about 10 minutes, about the amount of time needed to listen to three songs on your iPod. You decide to take a simple random sample of songs from a Billboard list of Rock Songs.31 Here is the list:Miss Murder Animal I Have Become Steady,
Ringtones for cell phones. You decide to change the ringtones for your cell phone by choosing 2 from a list of the 10 most popular ringtones.30 Here is the list:Super Mario Brothers Theme Sexy Love Ms. New Booty Ridin’ Rims I Write Sins Not Tragedies Gasolina My Humps The Pink Panther Down
Taxes and forestland usage. A study was designed to assess the impact of taxes on forestland usage in part of the Upper Wabash River Watershed in Indiana.29 A survey was sent to 772 forest owners from this region and 348 were returned. Consider the population, the sample, and the response rate for
Job satisfaction in Mongolian universities. A educational research team wanted to examine the relationship between faculty participation in decision making and job satisfaction in Mongolian public universities. They are planning to randomly select 300 faculty members from a list of 2500 faculty
Vitamin C for ultramarathon runners. An ultramarathon, as you might guess, is a footrace longer than the 26.2 miles of a marathon. Runners commonly develop respiratory infections after an ultramarathon. Will taking 600 milligrams of vitamin C daily reduce these infections? Researchers randomly
CHALLENGE Random digits. Table B is a table of random digits. Which of the following statements are true of a table of random digits, and which are false?Explain your answers.(a) There are exactly four 0s in each row of 40 digits.(b) Each pair of digits has chance 1/100 of being 00.(c) The digits
CH ALLENG E Calcium and the bones of young girls.Calcium is important to the bone development of young girls. To study how the bodies of young girls process calcium, investigators used the setting of a summer camp. Calcium was given in Hawaiian Punch at either a high or a low level.The camp diet
Carbon dioxide in the atmosphere. 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
Does oxygen help football players? We often see players on the sidelines of a football game inhaling oxygen. Their coaches think this will speed their recovery. We might measure recovery from intense exercise as follows: Have a football player run 100 yards three times in quick succession. Then
APPLET Use the simple random sample applet.The Simple Random Sample applet can demonstrate how randomization works to create similar groups for comparative experiments.Suppose that (unknown to the experimenters)the 20 even-numbered students among the 40 subjects for the cell phone study in Example
Five-digit zip codes and delivery time of mail.Does adding the five-digit postal zip code to an address really speed up delivery of letters? Does adding the four more digits that make up “zip + 4”speed delivery yet more? What about mailing a letter on Monday, Thursday, or Saturday? Describe the
The Monday effect on stock prices. Puzzling but true: stocks tend to go down on Mondays. There is no convincing explanation for this fact. A recent study looked at this “Monday effect” in more detail, using data on the daily returns of stocks on several U.S. exchanges over a 30-year period.
Saint-John’s-wort and depression. Does the herb Saint-John’s-wort relieve major depression? Here are some excerpts from the report of a study of this issue.24 The study concluded that the herb is no more effective than a placebo.(a) “Design: Randomized, double-blind, placebocontrolled
Treatment of pain for cancer patients. Health care providers are giving more attention to relieving the pain of cancer patients. An article in the jour Cancer surveyed a number of studies and concluded that controlled-release morphine tablets, which release the painkiller gradually over time, are
CHALLENGE Health benefits of bee pollen. “Bee pollen is effective for combating fatigue, depression, cancer, and colon disorders.” So says a Web site that offers the pollen for sale. We wonder if bee pollen really does prevent colon disorders. Here are two ways to study this question. Explain
CH ALLENGE Effectiveness of price discounts. Experiments with more than one factor allow insight into interactions between the factors. A study of the attractiveness of advertised price discounts had two factors: percent of all goods on sale (25%, 50%, 75%, or 100%) and whether the discount was
APPLET Use the simple random sample applet.The Simple Random Sample applet allows you to randomly assign experimental units to more than two groups without difficulty. Example 3.13(page 187) describes a randomized comparative experiment in which 150 students are randomly assigned to six groups of
APPLET Use the simple random sample applet.You can use the Simple Random Sample applet to choose a treatment group at random once you have labeled the subjects. Example 3.11 (page 185) uses Table B to choose 20 students from a group of 40 for the treatment group in a study of the effect of cell
Treatment of clothing fabrics. 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 minutes or 40 minutes; and a temperature of
Price cuts on athletic shoes. Stores advertise price reductions to attract customers. What type of price cut is most attractive? Market researchers prepared ads for athletic shoes announcing different levels of discounts (20%, 40%, 60%, or 80%). The student subjects who read the ads were also given
. Use a diagram to outline a completely randomized design for this experiment. Then do the randomization required to assign schools to treatments. If you use Table B, start at line 160.
Diagram the exercise and eating experiment.Twenty-four public middle schools agree to participate in the experiment described in Exercise
Guilt among workers who survive a layoff.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 90 students who were offered an opportunity to earn extra course credit by doing
Eye cataracts. Eye cataracts are responsible for over 40% of blindness worldwide. Can drinking tea regularly slow the growth of cataracts? We can’t experiment on people, so we use rats as subjects.Researchers injected 21 young rats with a substance that causes cataracts. One group of the rats
Smoking marijuana and willingness to work.How does smoking marijuana affect willingness to work? Canadian researchers persuaded people who used marijuana to live for 98 days in a “planned environment.” The subjects earned money by weaving belts. They used their earnings to pay for meals and
Chronic tension headaches. Doctors identify“chronic tension-type 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
Does aspirin prevent strokes and heart attacks?The Bayer Aspirin Web site claims that “Nearly five decades of research now link aspirin to the prevention of stroke and heart attacks.” The most important evidence for this claim comes from the Physicians’ Health Study, a large medical
Refusals in telephone surveys. 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
Will the students do more exercise and eat better? 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
How well do pine trees grow in shade? Ability to grow in shade may help pines in the dry forests of Arizona resist drought. How well do these pines grow in shade? Investigators planted pine seedlings in a greenhouse in either full light or light reduced to 5% of normal by shade cloth. At the end of
CHALLENGE Measuring water quality in streams and lakes. Water quality of streams and lakes is an issue of concern to the public. Although trained professionals typically are used to take reliable measurements, many volunteer groups are gathering and distributing information based on data that they
Compost tea. Compost tea is rich in microorganisms that help plants grow. It is made by soaking compost in water.16 Design a comparative experiment that will provide evidence about whether or not compost tea works for a particular type of plant that interests you. Be sure to provide all details

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