Most English professors complain that students don’t write very well. In particular they point out that students often confuse quality and quantity. A study at the University of Texas examined this claim. In the study undergraduate students were asked to compare the cost benefits of Japanese and American cars. All wrote their analyses on computers. Unbeknownst to the students, the computers were rigged so that some students would have to type twice as many words to fill a single page. The number of words used by each student was recorded. Can we conclude that students write in such a way as to fill the allotted space?
> The cost of health care is rising faster than most other items. To learn more about the problem a survey was undertaken to determine whether differences in health care expenditures exist between men and women. The survey randomly sampled men and women ag
> Because of the high cost of energy, homeowners in northern climates need to find ways to cut their heating costs. A building contractor wanted to investigate the effect on heating costs of increasing the insulation. As an experiment, he located a large s
> To determine the effect of advertising in the Yellow Pages, Bell Telephone took a sample of 40 retail stores that did not advertise in the Yellow Pages last year but did so this year. The annual sales (in thousands of dollars) for each store in both year
> Do waiters or waitresses earn larger tips? To answer this question, a restaurant consultant undertook a preliminary study. The study involved measuring the percentage of the total bill left as a tip for one randomly selected waiter and one randomly selec
> One measure of the state of the economy is the amount of money homeowners pay on their mortgage each month. To determine the extent of change between this year and 5 years ago, a random sample of 150 homeowners was drawn. The monthly mortgage payments fo
> The president of a large company is in the process of deciding whether to adopt a lunchtime exercise program. The purpose of such programs is to improve the health of workers and, in so doing, reduce medical expenses. To get more information, he institut
> In an effort to determine whether a new type of fertilizer is more effective than the type currently in use, researchers took 12 two-acre plots of land scattered throughout the county. Each plot was divided into two equal-size subplots, one of which was
> In a preliminary study to determine whether the installation of a camera designed to catch cars that go through red lights affects the number of violators, the number of red-light runners was recorded for each day of the week before and after the camera
> The operations manager of a manufacturer of television remote controls wants to determine which batteries last the longest in his product. He took a random sample of his remote controls and tested two brands of batteries. Here are the number of minutes o
> How effective are antilock brakes, which pump very rapidly rather than lock and thus avoid skids? As a test, a car buyer organized an experiment. He hit the brakes and, using a stopwatch, recorded the number of seconds it took to stop an ABS-equipped car
> Conduct a test to determine whether the two classifications L and M are independent, using the data in the accompanying cross-classification table. (Use  = .05.) M, M2 28 68 56 36
> Many people use scanners to read documents and store them in a Word (or some other software) file. To help determine which brand of scanner to buy, a student conducts an experiment wherein eight documents are scanned by each of the two scanners in which
> Suppose that you are analyzing one of the hundreds of statistical studies linking smoking with lung cancer. The study analyzed thousands of randomly selected people, some of whom had lung cancer. The statistics indicate that those who have lung cancer sm
> You wish to determine whether MBA graduates who majored in finance attract higher starting salaries than MBA graduates who majored in marketing. a. Describe a data-gathering process that produces observational data. b. Describe a data-gathering process t
> Put yourself in place of the director of research and development for a pharmaceutical company. When a new drug is developed it undergoes a number of tests. One of the tests is designed to determine whether the drug is safe and effective. Your company ha
> Suppose that you wish to test to determine whether one method of teaching statistics is better than another. a. Describe a data-gathering process that produces observational data. b. Describe a data-gathering process that produces experimental data.
> Refer to Exercise 13.24. a. Are the data observational or experimental? b. If the data are observational, describe a method of answering the question with experimental data? c. If the data are observational, produce another explanation for the statistica
> The owner of a small book-publishing company is concerned about the declining number of people who read books. To learn more about the problem she takes a random sample of customers in a retail book store and asked each how many books they read in the la
> A human resources manager for a car company wanted to know whether production-line workers have more days absent than office workers. He took a random sample of eight workers from each category and recorded the number of days absent the previous year. Ca
> For each of the following, determine the number of degrees of freedom assuming equal population variances and unequal population variances. a. n1 = 15, n2 = 15, s21 = 25, s22 = 15 b. n1 = 10, n2 = 16, s21 = 100, s22 = 15 c. n1 = 50, n2 = 50, s21 = 8, s22
> Is there enough evidence to draw the inference that drivers of convertibles are less likely to honk? Following car was Following car was not a convertible a convertible Honked horn 21 86 Did not honk 92 210 horn
> One factor in low productivity is the amount of time wasted by workers. Wasted time includes time spent cleaning up mistakes, waiting for more material and equipment, and performing any other activity not related to production. In a project designed to e
> Can we conclude from these statistics that women are less likely to honk? Following car driver was female Following car driver was male Honked horn 68 105 Did not honk horn 143 135
> Is there sufficient evidence to infer that drivers behind a male driver are more likely to honk? Lead car driver was female Lead car driver was male Honked horn 64 47 Did not honk horn 123 136
> Expensive Car Experiment Do these figures allow us to conclude that drivers behind expensive cars are less likely to honk? Lead car was expen- Lead car was not sive (over $50,Õ00) expensive Honked horn 33 49 Did not honk 122 118 horn
> Cell Phone Experiment 2 Can we conclude that male drivers are more likely to honk when the lead car driver is using a cell phone? Driver in following Lead car driver Lead car driver did car was male used cell phone not use cell phone Honked horn 35
> Cell Phone Experiment 1 Is there enough evidence to infer that women drivers in a following car are more likely to honk when the lead car driver is using a cell phone? Driver in following Lead car driver Lead car driver not car was female using cell
> According to the Canadian Cancer Society more than 21,000 women will be diagnosed with breast cancer every year and more than 5,000 will die. (U.S. figures are more than 10 times those in Canada.) Surgery is generally considered the first method of treat
> In Exercise 12.110, the statistics practitioner also recorded the gender of the respondents, where 1 = Female and 2 = Male. Can we infer that men and women differ in their choices of Christmas trees?
> In addition to recording whether faculty members who are between 55 and 64 plan to retire before they reach 65 in Exercise 12.105, the consultant asked each to report his or her annual salary. Can the president infer that professors aged 55 to 64 who pla
> In Exercise 12.35, we described how the office equipment chain OfficeMax offers rebates on some products. The goal in that exercise was to estimate the total amount spent by customers who bought the package of 100 CD-ROMS. In addition to tracking these a
> The objective in the survey conducted in Example 12.6 was to estimate the size of the market segment of adults who are concerned about eating healthy foods. As part of the survey each respondent was asked how much they spend on breakfast cereal in an ave
> A statistics professor is about to select a statistical software package for her course. One of the most important features, according to the professor, is the ease with which students learn to use the software. She has narrowed the selection to two poss
> In addition to asking about educational attainment the survey conducted in Exercise 12.131 also asked whether the respondent had plans in the next 2 years to take a course (1 = No, 2 = Yes). Can we conclude that Californians who did not complete high sch
> Movie studios segment their markets by age. Two segments that are particularly important to this industry are teenagers and 20- to 30-year-olds. To assess markets and guide the making of movies, a random sample of teenagers and 20- to 30-year-olds was dr
> The company that organized the survey to determine the amount of discarded newspaper (Example 12.1) kept track of the type of neighborhood (1 = City, 2 = Suburbs). Do these data allow the company management to infer that city households discard more news
> Exercise 12.31 dealt with the amount of time high school students spend per week at parttime jobs. In addition to the hours of part-time work the school guidance counselor recorded the gender of the student surveyed (1 = Female, 2 = Male). Can we conclud
> At a camp cafeteria teenagers were randomly given a tall skinny glass or a short wide glass. As they proceeded through the line they loaded up on the food they wanted and poured whatever drink they chose. At the end of the line the quantity of drink they
> Refer to Exercise 13.224. Customers were also asked how likely they would return to the restaurant (2 = Likely, 1 = Unlikely). Is there enough evidence to infer that when the restaurant features bright lights and loud music customers are less likely to r
> A television program in conjunction with a researcher conducted a makeover of a Hardee’s Restaurant. The main room had bright lights and loud music. In a separate room, the renovation brought in plants, paintings, indirect lighting, and white tablecloths
> A researcher convinced a restaurant to experiment with two different kinds of music. One was faster upbeat music and the second was soft relaxing music. A random sample of diners was drawn and the type of music, the amount of time spent in the restaurant
> Are Americans more generous than Canadians? Random samples of American and Canadian tax returns were examined and whether it included a charitable donation were recorded (2 = Yes, 1 = No). Conduct a statistical test to answer the question.
> Refer to Exercise 12.143. The researchers also took a random sample of 702 cars last year. Is there sufficient evidence to conclude that American cars this year are on average older than cars last year? Data from Exercise 12.143: An important factor in
> An important function of a firm’s human resources manager is to track worker turnover. As a general rule, companies prefer to retain workers. New workers frequently need to be trained, and it often takes time for new workers to learn how to perform their
> In 2005 Larry Summers, then president of Harvard University received an avalanche of criticism for his attempt to explain why in mathematics there are more male professors than female professors. His suggested that there were innate differences that migh
> An inspector for the Atlantic City Gaming Commission suspects that a particular blackjack dealer may be cheating (in favor of the casino) when he deals at expensive tables. To test her belief, she observed 500 hands each at the $100- limit table and the
> Medical experts advocate the use of vitamin and mineral supplements to help fight infections. A study undertaken by researchers at Memorial University recruited 96 men and women age 65 and older. One-half of them received daily supplements of vitamins an
> Many small retailers advertise in their neighborhoods by sending out flyers. People deliver these to homes and are paid according to the number of flyers delivered. Each deliverer is given several streets whose homes become their responsibility. One of t
> Approximately 20 million Americans work for themselves. Most run single-person businesses out of their homes. One-quarter of these individuals use personal computers in their businesses. A market research firm, Computer Intelligence InfoCorp, wanted to k
> There are currently 121,678 people waiting for lifesaving organ transplants in the United States. Of these, 100,791 await kidney transplants. (as of January 2016). The median wait time for an individual’s first kidney transplant is 3.6 years and can vary
> Personal spending is usually an indicator of the health of the overall economy. An increase tends to indicate that consumers are optimistic; a decrease indicates pessimism. Gallup tracks the spending of a random sample of American adults. The results for
> After observing the results of the test in Exercise 13.211, a statistics practitioner organized another experiment. People were matched according to gender, height, and weight. One member of each matched pair then exercised vigorously twice a week and th
> Most people exercise in order to lose weight. To determine better ways to lose weight, a random sample of male and female exercisers was divided into groups. The first group exercised vigorously twice a week. The second group exercised moderately four ti
> The Program for International Student Assessment (PISA) conducts tests of 15-year-olds. The tests jointly developed by the participating countries are tests for reading literary test, mathematical literacy test, and scientific literary test. Random sampl
> High blood pressure (hypertension) is a leading cause of strokes. Medical researchers are constantly seeking ways to treat patients suffering from this condition. A specialist in hypertension claims that regular aerobic exercise can reduce high blood pre
> Clinical depression is linked to several other diseases. Scientists at Johns Hopkins University undertook a study to determine whether heart disease is one of these. A group of 1190 male medical students was tracked over a 40-year period. Of these, 132 h
> Researchers at the University of Ohio surveyed 219 students and found that 148 had Facebook accounts. All students were asked how for their current GPA. Do the data allow us to infer that Facebook users have lower GPAs?
> The growing use of bicycles to commute to work has caused many cities to create exclusive bicycle lanes. These lanes are usually created by disallowing parking on streets that formerly allowed curbside parking. Merchants on such streets complain that the
> Refer to Exercise 13.205. Can we conclude that the defective rate differs between the two machines? Data from Exercise 13.205: Before deciding which of two types of stamping machines should be purchased, the plant manager of an automotive parts manufact
> Before deciding which of two types of stamping machines should be purchased, the plant manager of an automotive parts manufacturer wants to determine the number of units that each produces. The two machines differ in cost, reliability, and productivity.
> Have North Americans grown to distrust television and newspaper journalists? A study was conducted this year to compare what Americans currently think of the press versus what they said 3 years ago. The survey asked respondents whether they agreed that t
> In a study to determine whether gender affects salary offers for graduating MBA students, 25 pairs of students were selected. Each pair consisted of a female and a male student who were matched according to their GPAs, courses taken, ages, and previous w
> In designing advertising campaigns to sell magazines, it is important to know how much time each of a number of demographic groups spends reading magazines. In a preliminary study, 40 people were randomly selected. Each was asked how much time per week h
> An important component of the cost of living is the amount of money spent on housing. Housing costs include rent (for tenants), mortgage payments and property tax (for home owners), heating, electricity, and water. An economist undertook a 5-year study t
> As large cities grow larger, traffic congestion also increases. To measure how commuting time differs between California, New York, and Texas, random samples of commuters in each state were drawn. Is there sufficient evidence to infer that differences in
> Review the results of Exercises 15.1–15.3. What is the effect of decreasing the sample size?
> In recent years, a number of state governments have passed mandatory seat-belt laws. Although the use of seat belts is known to save lives and reduce serious injuries, compliance with seat-belt laws is not universal. In an effort to increase the use of s
> The city of Toronto boasts four daily newspapers. Not surprisingly, competition is keen. To help learn more about newspaper readers, an advertiser selected a random sample of people who bought their newspapers from a street vendor and people who had the
> Research scientists at a pharmaceutical company have recently developed a new nonprescription sleeping pill. They decide to test its effectiveness by measuring the time it takes for people to fall asleep after taking the pill. Preliminary analysis indica
> How important to your health are regular vacations? In a study a random sample of men and women were asked how frequently they take vacations. The men and women were divided into two groups each. The members of group 1 had suffered a heart attack; the me
> Every year, the Bureau of Labor Statistics administers a survey of American households called the American Time Use Survey. Respondents are asked to report their activities during an entire 24-hour day. The results are used to determine the number of hou
> A restaurant located in an office building decides to adopt a new strategy for attracting customers to the restaurant. Every week it advertises in the city newspaper. To assess how well the advertising is working, the restaurant owner recorded the weekly
> Obesity among children is quickly becoming an epidemic across North America. Television and video games are part of the problem. To gauge to what extent nonparticipation in organized sports contributes to the crisis surveys of children 5 to 14 years old
> Exercise 13.137 described the experiment that determined that taking aspirin daily reduces one’s probability of suffering a heart attack. The study was conducted in 1982 and at that time the mean age of the physicians was 50. In the years following the e
> In a study that was highly publicized, doctors discovered that aspirin seems to help prevent heart attacks. The research project, which was scheduled to last for 5 years, involved 22,000 American physicians (all male). Half took an aspirin tablet three t
> Plavix is a drug that is given to angioplasty patients to help prevent blood clots. A researcher at McMaster University organized a study that involved 12,562 patients in 482 hospitals in 28 countries. All the patients had acute coronary syndrome, which
> Refer to Exercise 12.131 where the statistics practitioner estimated the size of market segments based on education among California adults. Suppose that census figures from 10 years ago showed the education levels and the proportions of California adult
> Cold and allergy medicines have been available for a number of years. One serious side effect of these medications is that they cause drowsiness, which makes them dangerous for industrial workers. In recent years, a nondrowsy cold and allergy medicine ha
> The process that is used to produce a complex component used in medical instruments typically results in defective rates in the 40% range. Recently, two innovative processes have been developed to replace the existing process. Process 1 appears to be mor
> Surveys have been widely used by politicians around the world as a way of monitoring the opinions of the electorate. Six months ago, a survey was undertaken to determine the degree of support for a national party leader. Of a sample of 1,100, 56% indicat
> One hundred normal-weight people and 100 obese people were observed at several Chinese-food buffets. For each researcher recorded whether the diner used chopsticks or knife and fork. The table shown here was created. Is there sufficient evidence at the
> A firm has classified its customers in two ways: (1) according to whether the account is overdue and (2) whether the account is new (less than 12 months) or old. To acquire information about which customers are paying on time and which are overdue, a ran
> Many stores sell extended warranties for products they sell. These are very lucrative for store owners. To learn more about who buys these warranties a random sample of a store’s customers who recently purchased a product for which an e
> After sampling from two binomial populations we found the following. a. Estimate with 90% confidence the difference in population proportions. b. Repeat part (a) increasing the sample proportions to .48 and .52, respectively. c. Describe the effects of i
> These statistics were calculated from two random samples: a. Calculate the p-value of a test to determine whether there is evidence to infer that the population proportions differ. b. Repeat part (a) with p^1 = .95 and p^2 = .90. c. Describe the effect o
> Random samples from two binomial populations yielded the following statistics: a. Calculate the p-value of a test to determine whether we can infer that the population proportions differ. b. Repeat part (a) increasing the sample sizes to 400. c. Describe
> An important statistical measurement in service facilities (such as restaurants and banks) is the variability in service times. As an experiment, two bank tellers were observed, and the service times for each of 100 customers were recorded. Do these data
> Using the data supplied by NOAA National Weather Service, 19,450 tornadoes struck the United States between 2000 and 2014. The percentage for each month is listed here. The monthly number of tornadoes for 2015 was recorded. Is there enough statistical e
> In deciding where to invest her retirement fund, an investor recorded the weekly returns of two portfolios for 1 year. Can we conclude that portfolio 2 is riskier than portfolio 1?
> In Exercise 12.80 we described the problem of whether to change all the light bulbs at Yankee Stadium or change them one by one as they burn out. There are two brands of bulbs that can be used. Because both the mean and the variance of the lengths of lif
> A new highway has just been completed and the government must decide on speed limits. There are several possible choices. However, on advice from police who monitor traffic the objective was to reduce the variation in speeds, which it is thought to contr
> A statistics professor hypothesized that not only would the means vary, but also so would the variances if the business statistics course was taught in two different ways but had the same final exam. He organized an experiment wherein one section of the
> An operations manager who supervises an assembly line has been experiencing problems with the sequencing of jobs. The problem is that bottlenecks are occurring because of the inconsistency of sequential operations. He decides to conduct an experiment whe
> The manager of a dairy is in the process of deciding which of two new carton-filling machines to use. The most important attripute is the consistency of the fills. In a preliminary study she measured the fills in the 1-liter carton and listed them here.
> Random samples from two normal populations produced the following statistics: a. Estimate with 95% confidence the ratio of the two population variances. b. Repeat part (a) changing the sample sizes to n1 = 25 and n2 = 25. c. Describe what happens to the
> Random samples from two normal populations produced the following statistics: a. Can we infer at the 10% significance level that the two population variances differ? b. Repeat part (a) changing the sample sizes to n1 = 15 and n2 = 15. c. Describe what ha
> Refer to Example 13.2. The actual after and before operating incomes were recorded. a. Test to determine whether there is enough evidence to infer that for companies where an offspring takes the helm there is a decrease in operating income. b. Is there s
> Discuss why the experiment in Example 13.5 produced a significant test result whereas the one in Exercise 13.103 did not.
> From January 1 to December 31, 2011, there were 5,086 bank robberies in the United States. The percentage of that total for each day of the week is listed next. The number of robberies per day for the first two months of 2016 was recorded. Can we infer t
> Refer to Examples 13.4 and 13.5. Suppose that another experiment is conducted. Finance and marketing MBA majors were matched according to their undergraduate GPA. As in the previous examples, the highest starting salary offers were recorded. Can we infer
