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probability statistics
The Practice Of Statistics For Business And Economics 3rd Edition David S. Moore, George P. McCabe, Layth C. Alwan, Bruce A. Craig, William M. Duckworth - 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 the service they receive from a customer call center?(b) Do new
Price promotions and consumer expectations. A researcher studying the effect of price promotions on consumer 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 price
What’s wrong? Explain what is wrong in each of the following statements. Give reasons for your answers.(a) A simple random sample was used to assign a group of 30 subjects to three treatments.(b) It is better to use a table of random numbers to select a simple sample than it is to use a
Confidentiality at NORC (optional). The National Opinion Research Center conducts a large number of surveys and has established procedures for protecting the confidentiality of their survey participants. For their Survey of Consumer Finances, they provide a pledge to participants regarding
Online behavioral advertising (optional). The Federal Trade Commission Staff Report “Self-Regulatory Principles for Online Behavioral Advertising” defines behavioral advertising as “the tracking of a consumer’s online activities over time—including the searches the consumer has conducted,
Experiments and surveys for business. Write a short report describing the differences and similarities between experiments and surveys that would be used in business. Include a discussion of the advantages and disadvantages of each.
Deceiving subjects. A psychologist conducts the following experiment: she measures the attitude of subjects toward cheating, then has them play a game rigged so that winning without cheating is impossible. The computer that organizes the game also records—unknown to the subjects—whether or not
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
Asking teens about sex. The Centers for Disease Control and Prevention, in a survey of teenagers, asked the subjects if they were sexually active. Those who said “Yes” were then asked, “How old were you when you had sexual intercourse for the first time?” Should consent of parents be
AIDS trials in Africa. One of the most important goals of AIDS research is to find a vaccine that will protect against HIV infection. 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
How many have HIV? Researchers from Yale, working with medical teams in Tanzania, wanted to know how common infection with HIV, the virus that causes AIDS, is among pregnant women in that African country. To do this, they planned to test blood samples drawn from pregnant women.Yale’s
Student subjects. 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 subjects or to write a term paper.
Making poll results 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 release
Political polls. The presidential election campaign is in full swing, and the candidates have hired polling organizations to take sample surveys 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
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
Studying your 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
Facebook and academic performance. First Monday is a peer-reviewed journal on the Internet. They recently published two articles concerning Facebook and academic performance.Visit their Web site, firstmonday.org, and look at the first three articles in Volume 14, Number 5–4, May 2009. Identify
The Vytorin controversy. Vytorin is a combination pill designed to lower cholesterol. It consists of a relatively inexpensive and widely used drug, Zocor, and a newer drug called Zetia.Early study results suggested that Vytorin was no more effective than Zetia. Critics claimed that the makers of
How should the samples have been analyzed? Refer to the ovarian cancer diagnostic test study in Example 3.37(page 203). Describe howyouwould process the samples through the mass spectrometer.
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 being conducted in Africa are
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? You are a member 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
A sampling experiment. Figures 3.11 and 3.12 show how the sample proportion ˆp behaves when we take many samples from a population in which the population proportion is p = 0.6. You can follow the steps in this process on a small scale.Figure 3.16 is a small population. Each circle represents an
A sampling applet experiment. The Simple Random Sample applet can animate 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 100 individuals.
Sampling invoices. We will illustrate the idea of a sampling distribution in the case of a very small sample from a very small population. The population contains 10 past-due invoices.Here are the number of days each invoice is past due:Invoice: 0 1 2 3 4 5 6 7 8 9 Days past due: 8 12 10 5 7 3 15 9
Coin tossing. 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
Sampling in the states. The Internal Revenue Service plans to examine an SRS of individual federal income tax returns from each state. One variable of interest is the proportion of returns claiming itemized deductions. The total number of individual tax returns in a state varies from 14 million in
Bias and variability. Figure 3.15 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.
Sampling students. A management student is planning to take a survey of student attitudes toward part-time work while attending college. He develops a questionnaire and plans to ask 25 randomly selected students to fill it out. His faculty adviser approves the questionnaire but urges that the
Illustrate the idea of a sampling distribution. 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
UseTableBfor 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
Use statistical software for simulations. Statistical software can speed simulations. We are interested in the sampling distribution of the proportion ˆp of people who ate at a restaurant during the past week in an SRS from a population in which proportion p ate at a restaurant during the past
Simulate some coin tosses. 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 3.30 discusses sampling from a population in which proportion p = 0.6 (the parameter) ate in a restaurant during the
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 530,000 people in Wyoming to about 37 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
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
Ask more people. Just before a presidential election, a national opinion-polling firm increases the size of its weekly sample from the usual 1500 people to 4000 people.Why do you think the firm does this?
Inuit Survey. Inuit are the original inhabitants of the far north of what is now known as Canada. They live in an area known as Inuit Nunaat, which consists of four regions. These are the Inuvialt Region (in the Northwest Territories), Nunavut, Nunavik (north of the 55th parallel in the province of
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.
Simulation using random digits. You can use a table of random digits to simulate sampling from a population. Suppose that 60% of the population ate in a restaurant during the past week. That is, the population proportion is p = 0.6.(a) Let each digit in the table stand for one person in this
Consumer preference poll. A Web site asks viewers to choose which of two energy drinks they prefer. 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.34 Describe the sample and the population for this setting.
Survivor guilt in layoffs. 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 subject
Reaching Mexican Americans. Advertising that hopes to attract Mexican Americans must keep in mind the cultural orientation of these consumers. There are several psychological tests available to measure the extent to which Mexican Americans are oriented toward Mexican/Spanish or Anglo/English
Temperature and work performance. 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 20◦C (68◦F) and 30◦C (86◦F) as treatments. The response variable is the number of correct
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 percent of medical costs that are paid by health insurance has an effect either on the amount of medical
Aspirin and heart attacks. “Nearly five decades of research now link aspirin to the prevention of stroke and heart attacks.” So says the Bayer Aspirin Web site, www.bayeraspirin.com. The most important evidence for this claim comes from the Physicians’ Health Study, a large medical experiment
Marketing to children. If children are given more choices within a class of products, will they tend to prefer that product to a competing product that offers fewer choices? Marketers want to know. An experiment prepared three sets of beverages. Set 1 contained two milk drinks and two fruit drinks.
Should you charge a flat rate? You can use your computer to make telephone calls over the Internet. Howwill the cost affect the behavior of users of this service? You will offer the service to all 200 rooms in a college dormitory. Some rooms will pay a low flat rate. Others will pay higher rates at
Effects of price promotions. A researcher studying the effect of price promotions on consumers’ expectations makes up a history of the store price of a hypothetical brand of laundry detergent for the past year. Students in a marketing course view the price history on a computer. Some students see
Public housing. A study of the effect of living in public housing on the income and other variables in poverty-level households was carried out as follows. The researchers obtained a list of all applicants for public housing during the previous year.Some applicants had been accepted, while others
I’ll have a Mocha Light. Here’s the opening of a press release: “Starbucks Corp. on Monday said it would roll out a line of blended coffee drinks intended to tap into the growing popularity of reduced-calorie and reduced-fat menu choices for Americans.” You wonder if Starbucks customers
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%, or 60%). The student subjects who read the ads were also given
Drug use and willingness to work. How does smoking marijuana affect willingness to work? Canadian researchers persuaded young adult men who used marijuana to live for 98 days in a “planned environment.” The men earned money by weaving belts. They used their earnings to pay for meals and other
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 0000 can
Randomly assign the subjects. The Simple Random Sample applet allows you to randomly assign experimental units to more than two groups without difficulty. Example 3.25(page 178) describes a randomized comparative experiment in which 150 students are randomly assigned to six groups of 25.(a) Use the
Randomly assign the subjects. You can use the Simple Random Sample applet to choose a treatment group at random once you have labeled the subjects. Example 3.23(page 177) uses Table B to choose 20 students from a group of 40 for the treatment group in a study of the effect of cell phones on
Marketing your training materials. 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 collect.29 You are
Can you change attitudes of workers about teamwork?You will conduct an experiment designed to change attitudes of workers about teamwork. Discuss some variables that you might use if you were to use a block design for this experiment.3.66 An experiment for a new product. Compost tea is rich in
Evaluate a new method for training new employees. A new method for training new employees is to be evaluated by randomly assigning new employees to either the current training program or the new method. A questionnaire will be used to evaluate the satisfaction of the new employees with the
What is wrong? Explain what is wrong with each of the following randomization procedures and describe howyouwould do the randomization correctly.(a) A list of 50 subjects is entered into a computer file and then sorted by last name. The subjects are assigned to five treatments by taking the first
What is needed? Explain what is deficient in each of the following proposed experiments and explain how you would improve the experiment.(a) Two forms of a lab exercise are to be compared. There are 10 rows in the classroom. Students who sit in the first 5 rows of the class are given the first
Does charting help investors? Some investment advisers 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
Frustration and teamwork. 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 laboratory, and has them play a game that requires teamwork. The game is rigged so that they
Managers and stress. Some companies employ consultants to train their managers in meditation in the hope that this practice will relieve stress and make the managers more effective on the job. An experiment that claimed to show that meditation reduces anxiety proceeded as follows. The experimenter
Do the randomization. Use computer software to carry out the randomization in Example 3.25.
Statistical significance. The financial aid office of a university asks a sample of students about their employment and earnings. The report says that “for academic year earnings, a significant difference was found between the sexes, with men earning more on the average. No significant difference
Exercise and heart attacks. Does regular exercise reduce the risk of a heart attack? Here are two ways to study this question. Explain clearly why the second design will produce more trustworthy data.1. A researcher finds 2000 men over 40 who exercise regularly and have not had heart attacks. She
Utility companies. Example 3.21 describes an experiment to learn whether providing households with electronic meters or charts will reduce their electricity consumption.An executive of the utility company objects to including a control group. He says, “It would be simpler to just compare
Does child care help recruit employees? Will providing child care for employees make a company more attractive to women, even those who are unmarried? You are designing an experiment to answer this question. You prepare recruiting material for two fictitious companies, both in similar businesses in
Sealing food packages. Use a diagram to describe a completely randomized experimental design for the package liner experiment of Exercise 3.48. (Show the size of the groups, the treatment each group receives, and the response variable. Figures 3.6 and 3.7 are models to follow.) Use software or
Gastric freezing. Example 3.19 describes an experiment that helped end the use of gastric freezing to treat ulcers. The subjects were 160 ulcer patients.(a) Make a diagram to outline the design of this experiment, using the information in Example 3.19. (Show the size of the groups, the treatment
Diagram the Web use. Refer to Exercise 3.47 (page 170). Draw a diagram similar to Figure 3.5 that describes the computer graphics drawing experiment.
Diagram the food storage experiment. Refer to Exercise 3.46 (page 170). Draw a diagram similar to Figure 3.5 that describes the food for space travel experiment.
Does using statistical software improve exam scores? An instructor in an elementary statistics course wants to know if using a new statistical software package will improve students’ final-exam scores. He asks for volunteers and about half of the class agrees to work with the new software. He
Is the packaging convenient for the customer? A manufacturer of food products uses package liners that are sealed at the top by applying heated jaws after the package is filled. The customer peels the sealed pieces apart to open the package. What effect does the temperature of the jaws have on the
Can they use the Web? A course in computer graphics technology requires students to learn multiview drawing concepts. This topic is traditionally taught using supplementary material printed on paper. The instructor of the course believes that a Web-based interactive drawing program will be more
Radiation and storage time for food products. Storing food for long periods of time is a major challenge for those planning for human space travel beyond the moon.One problem is that exposure to radiation decreases the length of time that food can be stored. One experiment examined the effects of
Economic attitudes of Spaniards. Spain’s Centro de Investigaciones Sociol´ogicos carried out a sample survey on the economic attitudes of Spaniards.21 Of the 2496 adults interviewed, 72% agreed that “employees with higher performance must get higher pay.” On the other hand, 71% agreed that
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.
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 Bureau of the Census, in 2008, families that have children average 1.86 children. Why is a sample like this
When do you ask? When observations are taken over time, it is important to check for patterns that may be important for the interpretation of the data. In Section 1.1 we learned to use a time plot for this purpose. Describe and discuss a sample survey question where you would expect to have
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
Select employees for an awards committee. A department has 30 hourly workers and 10 salaried workers. The hourly workers areand the salaried workers are Andrews Fernandez Kim Moore Rabinowitz Besicovitch Gupta Lightman Phillips Yang The committee will have 6 hourly workers and 2 salaried
Stratified samples of forest areas in the Amazon basin.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
Random digit telephone dialing for market research. A market research firm 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
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 3.33 asks you to choose an SRS of blocks from the census tract pictured in Figure 3.4. 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, 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
Select a simple random sample. There are approximately 380 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 codes 001 to
Select a simple random sample. 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.APPLET
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 classify regions of each field as either healthy mint, diseased mint, or weed-infested mint. The GIS divides
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