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The Practice Of Statistics For Business And Economics 4th Edition Layth C. Alwan, Bruce A. Craig - Solutions

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. Candidates for public office hire polling organizations to take sample surveys to find out what the voters think about the issues. What information should the pollsters be required to disclose?(a) What does the standard of informed consent require the pollsters to tell potential
Anonymous? Confidential? 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 learn the results of the test
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 when you were treated for 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. It recently published two articles concerning Facebook and academic performance. Visit its website, firstmonday.org, and look at the first three articles in Volume 14, Number 5–4, May 2009. Identify the
The Vytorin controversy. Vytorin is a combination pill designed to lower cholesterol.The combination 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
How should the samples been analyzed?Refer to the ovarian cancer diagnostic test study in Example 3.33 (page 165). Describe how you would process the samples through the mass spectrometer.
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 of a large medical clinic were to be randomly assigned to treatment and control groups. The treatment group would be offered
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
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 this
Should we allow this personal information to be collected? In which of the following circumstances 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
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
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
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 20oC (68oF) and 30oC (86oF) as treatments. The response variable is the number of correct insertions,
Effects of TV advertising. You decide to use a completely randomized design in the two-factor experiment on response to advertising described in Example 3.16 (page 143). The 30 students named below will serve as subjects. Outline the design. Then use software or Table B at line 110 to randomly
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
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 website, bayeraspirin.com. The most important evidence for this claim comes from the Physicians’ Health Study, a large medical experiment
Effects of price promotions. A researcher is studying the effect of price promotions on consumers’expectations. She 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
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
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
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) Each pair of digits has chance 1/100 of being 50.(b) There are exactly four 0s in each row of 40 digits.(c) The digits 9999 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 3.23 (page 152) describes a randomized comparative experiment in which 150 students are randomly assigned to six groups of 25.(a) Use
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 3.22 (page 151) describes an experiment in which 20 students are chosen from a group of 40 for the treatment group in a study of the effect of
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.26 You are
An experiment for a new product. Compost tea is rich in microorganisms that help plants grow.It is made by soaking compost in water.25 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
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.
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 training.
What is wrong? Explain what is wrong with each of the following randomization procedures, and describe how you would 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
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 five 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 3.23.
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
Utility companies. Example 3.19 (page 147) 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
Sealing food packages. Use a diagram to describe a completely randomized experimental design for the package liner experiment of Exercise 3.44 (page 145).(Show the size of the groups, the treatment each group receives, and the response variable. Figures 3.5 and 3.6 are models to follow.) Use
Does child care help recruit employees? Will providing child care for employees make a company more attractive to women? You are designing an experiment to answer this question. You prepare recruiting material for two fictitious companies, both in similar businesses in the same location. Company
Diagram the Web use. Refer to Exercise 3.43 (page 144). Draw a diagram similar to Figure 3.5 that describes the computer graphics drawing experiment.
Diagram the food storage experiment. Refer to Exercise 3.42 (page 144).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 approximately half of the class agrees to work with the new
Is the packaging convenient for the customer? A manufacturer of food products uses package liners that are sealed 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 force needed
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
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
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 1.2 (page 19), we learned to use a time plot for this purpose. Describe and discuss a sample survey question where you would expect to
Select employees for an awards committee. A department has 30 hourly workers and 10 salaried workers. The hourly workers 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
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. 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 four addresses out
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?
Select a simple random sample. There are approximately 446 active telephone area codes covering Canada, the United States, and some Caribbean areas.19 (More are created regularly.) You want to choose an SRS of 30 of these area codes for a study of available telephone numbers. Use software or the
Select a simple random sample. After you have labeled the cases 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 classify regions of each field as either healthy mint, diseased mint, or weed-infested mint. The GIS divides
Interview potential customers. You have been hired by a company that is planning to build a new apartment complex for students in a college town. They want you to collect information about preferences of potential customers for their complex. Most of the college students who live in apartments live
Identify the populations. For each of the following sampling situations, identify the population as exactly as possible. That is, indicate what kind of cases the population consists of and exactly which cases fall in the population. If the information given is not complete, complete the description
Popularity of news personalities can affect market share. A Gallup Poll conducted telephone interviews with 1001 U.S. adults aged 18. One of the questions asked whether the respondents had a favorable or an unfavorable opinion of 17 news personalities.Diane Sawyer received the highest rating, with
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 120 businesses at random. Of these, 54 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 statements.(a) A simple random sample is the only way to randomly select cases from a population.(b) Random digits cannot be used to select a sample from a population that has more than 100 cases.(c) The population consists of all cases
Random digit dialing. The list of cases from which a sample is actually selected is called the sampling frame. Ideally, the frame should include every case in the population, but in practice this is often difficult. A frame that leaves out part of the population is a common source of
Sampling by accountants. 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 5000 accounts
Who goes to the market research workshop? A small advertising firm has 30 junior associates and 10 senior associates. The junior associates are Abel Fisher Huber Miranda Reinmann Chen Ghosh Jimenez Moskowitz Santos Cordoba Griswold Jones Neyman Shaw David Hein Kim O’Brien Thompson Deming
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 the top 10 songs listed on the Billboard Top Heatseekers Songs.13 Here is the list:Studio
Ringtones for cell phones. You decide to change the ringtones for your cell phone by choosing two from a list of the 10 most popular ringtones.12 Here is the list:Fancy Happy Turn Down for What Rude Problem Bottoms Up All of Me Crise Beachin’ Wiggle Select your two ringtones using a simple random
Market segmentation and movie ratings. You wonder if that new“blockbuster” movie is really any good. Some of your friends like the movie, but you decide to check the Internet Movie Database (imdb.com) to see others’ratings. You find that 2497 people chose to rate this movie, with an average
What is the population? For each of the following sampling situations, identify the population as exactly as possible. That is, indicate what kind of cases the population consists of and exactly which cases fall in the population.If the information given is not sufficient, complete the description
Job satisfaction. A research team wanted to examine the relationship between employee participation in decision making and job satisfaction in a company. They are planning to randomly select 300 employees from a list of 2500 employees in the company. The Job Descriptive Index (JDI) will be used to
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.9 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
Are there treatments? Refer to Exercises 3.9 through 3.15. For any of these that involve an experiment, describe the treatment that is used.
Does job training work? A state institutes a job-training program for manufacturing workers who lose their jobs. After five years, the state reviews how well the program works. Critics claim that because the state’s unemployment rate for manufacturing workers was 6% when the program began and 10%
Is the product effective? An educational software company wants to compare the effectiveness of its computer animation for teaching about supply, demand, and market clearing with that of a textbook presentation. The company tests the economic knowledge of 50 first-year college students, then
Gender and consumer choices. Men and women differ in their choices for many product categories. Are there gender differences in preferences for health insurance plans as well? A market researcher interviews a large sample of consumers, both men and women. She asks each consumer which of two health
Satisfaction with allocation of concert tickets.Your college sponsored a concert that sold out.(a) After the concert, an article in the student newspaper reported interviews with three students who were unable to get tickets and were very upset with that fact.What kind of data does this represent?
Marketing milk. An advertising campaign was developed to promote the consumption of milk by adolescents. Part of the campaign was based on a study conducted to determine the effect of additional milk in the diet of adolescents over a period of 18 months. A control group received no extra
Claims settled for $3,300,000! According to a story in Consumer Reports, three major producers of canned tuna agreed to pay $3,300,000 to settle claims in California that the amount of tuna in their cans was less than the amount printed on the label of the cans.6 What kind of data do you think was
A dissatisfied customer. You like to eat tuna sandwiches. Recently you noticed that there does not seem to be as much tuna as you expected when you opened the can. Identify the type of data that this represents, and describe how it can or cannot be used to reach a conclusion about the amount of
An advertising agency chooses an ESPN television ad. An advertising agency developed two versions of an ad that will be shown during a major sporting event on EPSN but must choose only one to air. The agency recruited 100 college students and divided them into two groups of 50. Each group viewed
Market share for energy drinks. A website reports that Red Bull is the top energy drink brand with sales of $2.9 billion in 2014.5 Do you think that this report is based on an observational study or an experiment? Explain your answer.
Are Millennials loyal customers? A website claims that Millennial generation consumers are very loyal to the brands that they prefer. What additional information do you need to evaluate this claim?
Reliability of a product. A friend has driven a Toyota Camry for more than 200,000 miles with only the usual service maintenance expenses. Explain why not all Camry owners can expect this kind of performance.
Preference for a brand. Samantha is a serious runner. She and all her friends prefer drinking Gatorade Endurance to Heed prior to their long runs. Explain why Samantha’s experience is not good evidence that most young people prefer Gatorade Endurance to Heed.
Should you invest in stocks? You have just accepted a new job and are offered several options for your retirement account. One of these invests about 75% of your employer’s contribution in stocks. You talk to a friend who joined the company several years ago who said that after he chose that
Is this good market research? You and your friends are big fans of True Detective, an HBO police drama. To what extent do you think you can generalize your preference for this show to all students at your college?
Recycled product quality. Recycling is supposed to save resources. Some people think recycled products are lower in quality than other products, a fact that makes recycling less practical. People who actually use a recycled product may have different opinions from those who don’t use it. Here are
More smokers live at least 20 more years!You can see the headlines “More smokers than nonsmokers live at least 20 more years after being contacted for study!’’ A medical study contacted randomly chosen people in a district in England. Here are data on the 1314 women contacted who were either
Aspirin and heart attacks. Does taking aspirin regularly help prevent heart attacks? “Nearly five decades of research now link aspirin to the prevention of stroke and heart attacks.’’ So says the Bayer Aspirin website, bayeraspirin.com. The most important evidence for this claim comes from
Wood products. A wood product manufacturer is interested in replacing solid-wood building material by less-expensive products made from wood flakes.27 The company collected the following data to examine the relationship between the length (in inches) and the strength (in pounds per square inch) of
Simpson’s paradox and regression. Simpson’s paradox occurs when a relationship between variables within groups of observations reverses when all of the data are combined. The phenomenon is usually discussed in terms of categorical variables, but it also occurs in other settings. Here is an
What correlation does and doesn’t say.Construct a set of data with two variables that have different means and correlation equal to one. Use your example to illustrate what correlation does and doesn’t say.
Circular saws. The table in the previous exercise gives the weight (in pounds) and amps for 19 circular saws. The data contain only five different amp ratings among the 19 saws. CIRCSAW(a) Calculate the correlation between the weights and the amps of the 19 saws.(b) Calculate the average weight of
Circular saws. The following table gives the weight (in pounds) and amps for 19 circular saws.Saws with higher amp ratings tend to also be heavier than saws with lower amp ratings. We can quantify this fact using regression.Weight Amps Weight Amps Weight Amps 11 15 9 10 11 13 12 15 11 15 13 14 11
Look at the data for men. Refer to the previous exercise. Analyze the data for the men’s team from the same college, and compare your results with those for the women.
Points scored in women’s basketball games. Use the Internet to find the scores for the past season’s women’s basketball team at a college of your choice. Is there a relationship between the points scored by your chosen team and the points scored by their opponents? Summarize the data and
Planning for a new product. The editor of a statistics text would like to plan for the next edition.A key variable is the number of pages that will be in the final version. Text files are prepared by the authors using a word processor called LaTeX, and separate files contain figures and tables. For
Marketing your college. Colleges compete for students, and many students do careful research when choosing a college. One source of information is the rankings compiled by U.S.News & World Report. One of the factors used to evaluate undergraduate programs is the proportion of incoming students who
Bigger raises for those earning less. Refer to the previous two exercises. The 2014–2015 salaries do an excellent job of predicting the 2015–2016 salaries.Is there anything more that we can learn from these data? In this department, there is a tradition of giving higher-than-average percent
Find the line and examine the residuals.Refer to the previous exercise. FACSAL(a) Find the least-squares regression line for predicting 2015–2016 salaries from 2014–2015 salaries.(b) Analyze the residuals, paying attention to any outliers or influential observations. Write a summary of your

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