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business
business statistics a first course

Questions and Answers of Business Statistics A First Course

11.56 In a study by the United Dairy Industry Association, 42% of 655 persons age 35–44 said they seldom or never ate cottage cheese. For 455 individuals age 45–54, the corresponding percentage
11.55 In examining the ability of users to complete a variety of information-seeking tasks on their mobile devices, Nielsen Norman Group assigned sample members to get the answers to a variety of
11.54 A bank manager has been presented with a new brochure that was designed to be more effective in attracting current customers to a personal financial counseling session that would include an
11.53 Summary data for two independent samples are p1 5 0.31, n1 5 400, and p2 5 0.38, n2 5 500. Use the 0.05 level of significance in testing H0: 1 5 2 versus H1: 1 Þ 2.
11.52 Summary data for two independent samples are p1 5 0.36, n1 5 150, and p2 5 0.29, n2 5 100. Use the 0.025 level of significance in testing H0: 1 # 2 versus H1: 1 . 2.
11.51 A plant manager has collected productivity data for a sample of workers, intending to see whether there is a difference in the number of units they produce on Monday versus Thursday. The
11.50 For a special pre–New Year’s Eve show, a radio station personality has invited a small panel of prominent local citizens to help demonstrate to listeners the adverse effect of alcohol on
11.49 The students in an aerobics class have been weighed both before and after the 5-week class, with the following results:Using the 0.05 level of significance, evaluate the effectiveness of the
11.48 In an attempt to measure the emotional effect of a proposed billboard ad, an advertising agency checks the pulse rate of 10 persons before and after they are shown a photograph of the
11.47 A trucking firm is considering the installation of a new, low-restriction engine air filter for its long-haul trucks, but doesn’t want to make the switch unless the new filter can be shown to
11.46 A university president randomly selects 10 tenured faculty from the College of Arts and Sciences and 10 tenured faculty from the College of Business. Each faculty member is then asked to rate
11.45 Each of 20 consumers is provided with a package containing two different brands of instant coffee.A week later, they are asked to rate the taste of each coffee on a scale of 1 (poor taste) to
11.44 A pharmaceutical firm has checked the cholesterol levels for each of 30 male patients, then provided them with fish-oil capsules to take on a daily basis. The cholesterol levels are rechecked
11.43 A study has been conducted to examine the effectiveness of a new experimental program for preparing high school students for the Scholastic Aptitude Test.Eighty students have been randomly
11.42 In planning the processes to be incorporated into a new manufacturing facility, engineers have proposed two possible assembly procedures for one of the phases in the production sequence. Sixty
11.41 In their 2003 and 2008 studies on how long wireless customers have to spend on hold before speaking with a customer service representative, J.D. Power and Associates found the mean times to be
11.40 According to a psychologist at the Medical College of Virginia, soccer players who “head” the ball 10 or more times a game are at risk for brain damage that could lower their intellectual
11.39 A study found that women of normal weight missed an average of 3.4 days of work due to illness during the preceding year, compared to an average of 5.2 days for women who were considered
11.38 A study of 102 patients who had digestive-tract surgery found that those who chewed a stick of gum for 15 minutes at mealtimes ended up being discharged after an average of 4.4 days in the
11.37 Surveys of dog owners in two adjacent towns found the average veterinary-related expense total for dog owners in town A during the preceding year was$240, with a standard deviation of $55,
11.36 According to the U.S. Bureau of Labor Statistics, personal expenditures for entertainment fees and admissions averaged $349 per person in the Northeast and$420 in the West. Assuming that these
Repeat Exercise 11.21 using the z-test approximation to the unequal-variances t-test.
Repeat Exercise 11.20 using the z-test approximation to the unequal-variances t-test.
For the following independent random samples, use the z-test and the 0.05 level of significance in testing H0: 1 # 2 versus H1: 1 . 2.}x 1 5 85.2 s1 5 9.6 n1 5 40}x 2 5 81.7 s2 5 4.1 n2 5 32
For the following independent random samples, use the z-test and the 0.01 level of significance in testing H0: 1 5 2 versus H1: 1 ? 2.}x 1 5 33.5 s1 5 6.4 n1 5 31}x 2 5 27.6 s2 5 2.7 n2 5 30
Under what conditions is it appropriate to use the z-test as an approximation to the unequal-variances t-test when comparing two sample means?
11.30 During May 2009, visitors to usatoday.com spent an average of 12.2 minutes per visit, compared to 11.0 minutes for visitors to washingtonpost.com. Assuming that file XR11030 contains the sample
11.29 It has been reported that the average visitor from Japan spent $3120 during a trip to the United States, while the average for a visitor from the United Kingdom was$2654. Assuming that file
11.28 When companies are designing a new product, one of the steps typically taken is to see how potential buyers react to a picture or prototype of the proposed product. The product-development team
11.27 According to a Yankelovich poll, women spend an average of 19.1 hours shopping during the month of December, compared to 12.7 hours for men. Assuming that file XR11027 contains the survey data
11.26 One of the measures of the effectiveness of a stimulus is how much the viewer’s pulse rate increases on exposure to it. In testing a lively new music theme for its television commercials, an
11.25 According to a national Gallup poll, men visit the doctor’s office an average of 3.8 times per year, while women visit an average of 5.8 times per year. In a similar poll conducted in a
11.24 Safety engineers at a manufacturing plant are evaluating two brands of 50-ampere electrical fuses for possible purchase and use in the plant. One of the performance characteristics they are
11.23 The credit manager for Braxton’s Department Store, in examining the accounts for various types of customers served by the establishment, has noticed that the mean outstanding balance for a
11.22 A tire company is considering switching to a new type of adhesive designed to improve tire reliability in high-temperature and overload conditions. In laboratory“torture” tests with
11.21 Fred and Martina, senior agents at an airline security checkpoint, carry out advanced screening procedures for hundreds of randomly selected passengers per day. For a random sample of 30
In two independent samples, 2x 1 5 125.0, s1 5 21.5, n1 5 40, and 2x 2 5 116.4, s2 5 10.8, n2 5 35.Using the 0.025 level of significance, test H0: 1 # 2 versus H1: 1 . 2.
In two independent samples, 2x 1 5 165.0, s1 5 21.5, n1 5 40 and 2x 2 5 172.9, s2 5 31.3, n2 5 32.Using the 0.10 level of significance, test H0: 1 $ 2 versus H1: 1 , 2.
In two independent samples from populations that are normally distributed, 2x 1 5 35.0, s1 5 5.8, n1 5 12 and 2x 2 5 42.5, s2 5 9.3, n2 5 14. Using the 0.05 level of significance, test H0: 1 5 2
11.17 Using the sample results in Exercise 11.16, construct and interpret the 95% confidence interval for the difference between the population means. Is the hypothesized difference (0.00) within the
11.16 An engineer has measured the hardness scores for a sample of conveyor-belt support bearings that have been hardened by two different methods. The first method is used by her company, and the
11.15 Using the sample results in Exercise 11.14, construct and interpret the 95% confidence interval for the difference between the population means. Is the hypothesized difference (0.00) within the
11.14 Comparing the number of Facebook “friends” for men and women, observers have speculated about whether the mean number of friends could be the same for each group. Assume that data file
11.13 It has been claimed that flattening (“rolling”) the barrel of a graphite baseball bat can stretch the fibers and result in a pitched baseball being returned faster than with a regulation
11.12 A study published in the Archives of Internal Medicine examined the prevalence of so-called “difficult”patients who ask for unneeded prescriptions, unnecessarily complain, or otherwise
A nutritionist has noticed a FoodFarm ad stating the company’s peanut butter contains less fat than that produced by a major competitor. She purchases 11 8-ounce jars of each brand and measures the
11.10 In a test of the effectiveness of a new battery design, 16 battery-powered music boxes are randomly provided with either the old design or the new version. Hours of playing time before battery
11.9 Media observers have been examining the number of minutes devoted to business and financial news during the half-hour evening news broadcasts of two local television channels. For each channel,
11.8 Sheila Smith, the manager of a large resort’s main hotel, has been receiving complaints from some guests that they are not being provided with prompt service upon approaching the front desk.
11.7 Comparing dexterity-test scores of workers on the day shift versus those on the night shift, the production manager of a large electronics plant finds that a sample of 37 workers from the day
11.6 A sample of 40 investment customers serviced by an account manager are found to have had an average of $23,000 in transactions during the past year, with a standard deviation of $8500. A sample
11.5 A maintenance supervisor is comparing the standard version of an instructional booklet with one that has been claimed to be superior. An experiment is conducted in which 26 technicians are
11.4 An ambulance service located at the edge of town is responsible for serving a large office building in the downtown area. Testing different routes for getting from the ambulance station to the
11.3 Using independent random samples, a researcher is comparing the number of hours of television viewed last week for high school seniors versus sophomores. The results are shown here. Assuming
11.2 An educator is considering two different videotapes for use in a half-day session designed to introduce students to the basics of economics. Students have been randomly assigned to two groups,
“When comparing two sample means, the t-test should be used only when the sample sizes are less than 30.” Comment.
Set the right and bottom sliders so that n 5 20 and 5 11.2. Now move the left slider upward and downward to change the level for the test. Observe the power of the test for each of the following
Set the left and bottom sliders so that 5 0.05 and 5 11.2. Now move the right slider upward and downward to change the sample size for the test. Observe the power of the test for each of the
Set the left, right, and bottom sliders so that 5 0.05, n 5 15, and 5 the same value you selected in Applet Exercise 13.1. Now move the left slider upward and downward to change the level for
Using the left and right sliders, set up the test so that 5 0.10 and n 5 20. Now move the bottom slider so that the actual is as close as possible to 10 without being equal to 10 (e.g., 10.01).
Using the slider, decrease the sample mean to approximately 1.310 minutes. Based on this confidence interval, would it seem believable that the true population mean might be 1.325 minutes?
Using the slider, increase the sample mean to approximately 1.330 minutes. What is the 95% confidence interval for ? Based on this confidence interval, would it seem believable that the true
When the applet initially loads, identify the sample mean and describe the 95% confidence interval for .Based on this confidence interval, would it seem believable that the true population mean
If Springdale Mall offered exactly the same benefits as the other two shopping areas, we would expect exactly one-third of those who expressed an opinion to select it as the area best fitting the
Item C in the description of the data collection instrument lists variables 7, 8, and 9, which represent the respondent’s general attitude toward each of the three shopping areas. Each of these
In the past, the mean lifetime of diesel engine injection pumps has been 12,000 operating hours. A new injection pump is available that is promoted as lasting longer than the old version. In a test
Use the decision rule associated with Exercise 10.111 and a range of selected assumed values for to construct the power curve for the test.
In making aluminum castings into alternator housings, an average of 3.5 ounces per casting must be trimmed off and recycled as a raw material.A new manufacturing procedure has been proposed to reduce
Based on the sample results in Exercise 10.109, construct and interpret the 95% confidence interval for the population proportion. Is the hypothesized proportion(0.25) within the interval? Given the
According to the U.S. Department of Justice, 25% of violent crimes involve the use of a weapon. We will assume that data file XR10109 contains a sample of the crime information for a given city, with
Before installing a high-tech laser exhibit near the exit area, a museum of American technology found the average contribution by patrons was $2.75 per person.For a sample of 30 patrons following
Historically, Shop-Mart has gotten an average of 2000 hours of use from its G&E fluorescent lightbulbs.Because its fixtures are attached to the ceiling, the bulbs are rather cumbersome to replace,
A consumer agency suspects that a pet food company may be underfilling packages for one of its brands. The package label states “1600 grams net weight,” and the president of the company claims
In an interview with a local newspaper, a respected trial lawyer claims that he wins at least 75% of his court cases. Bert, a skeptical statistics student, sets up a one-tail test at the 0.05 level
A national chain of health clubs says the mean amount of weight lost by members during the past month was at least 5 pounds. Skeptical of this claim, a consumer advocate believes the chain’s
An exterminator claims that no more than 10%of the homes he treats have termite problems within 1 year after treatment. In a sample of 100 homes, local officials find that 14 had termites less than 1
In a taste comparison test, it was found that 58 of 100 persons preferred the chunky version of a peanut butter over the creamy type. An interested observer would like to determine whether this
The administrator of a local hospital has told the governing board that 30% of its emergency room patients are not really in need of emergency treatment (i.e., the problems could just as easily have
A 1931 issue of Time magazine contained an advertisement for Liberty magazine. According to a study cited by Liberty, it was found that 15% of Liberty families had a “mechanical refrigerator,”
During 2006, 3.0% of all U.S. households were burglary victims. For a simple random sample of 300 households from a certain region, suppose that 18 households were victimized by burglary during that
A state transportation official claims that the mean waiting time at exit booths from a toll road near the capitol is no more than 0.40 minutes. For a sample of 35 motorists exiting the toll road, it
A regional office of the Internal Revenue Service randomly distributes returns to be audited to the pool of auditors. Over the thousands of returns audited last year, the average amount of extra
Technical data provided with a room dehumidifier explain that units tested from the production line consume a mean of 800 watts of power, with a standard deviation of 12 watts. The superintendent of
10.95 The average U.S. household has $235,600 in life insurance. A local insurance agent would like to see how households in his city compare to the national average, and selects a simple random
10.94 The average U.S. family includes 3.13 persons. To determine whether families in her city tend to be representative in size compared to those across the United States, a city council member
10.93 Before the hiring of an efficiency expert, the mean productivity of a firm’s employees was 45.4 units per hour, with a standard deviation of 4.5 units per hour.After incorporating the changes
10.92 Before accepting a large shipment of bolts, the director of an elevator construction project checks the tensile strength of a simple random sample consisting of 20 bolts.She is concerned that
10.91 Strands of human hair absorb elements from the bloodstream and provide a historical record of both health and the use or nonuse of chemical substances. Hair grows at the rate of about one-half
10.90 For each of the following situations, determine whether a one-tail test or a two-tail test would be appropriate. Describe the test, including the null and alternative hypotheses, then explain
Plot the operating characteristic curve that corresponds to the power curve constructed for Exercise 10.86.
Plot the operating characteristic curve that corresponds to the power curve constructed for Exercise 10.84.
When a thread-cutting machine is operating properly, only 2% of the units produced are defective. Since the machine was bumped by a forklift truck, however, the quality-control manager is concerned
Using assumed true population means of 2.80, 2.85, 2.90, 2.95, and 3.00 hours, plot the power curve for the test in Exercise 10.32.10.86 Using assumed true population percentages of 2%, 3%, 4%, 5%,
Using assumed true population means of 2.485, 2.490, 2.495, 2.500, 2.505, 2.510, and 2.515 inches, plot the power curve for the test in Exercise 10.31.
For the test described in Exercise 10.32, assume that the true population mean for the new booklet is 5 2.80 hours. Under this assumption, what is the probability that the false null hypothesis, H0:
For the test described in Exercise 10.31, if the true population mean is really 2.520 inches, what is the probability that the inspector will correctly reject the false null hypothesis that 5 2.500
A hypothesis test has been set up and is to be con ducted at the 5 0.05 level of significance. If the sample size is doubled, what will be the effect on ?
What is an operating characteristic curve and how is it related to the power curve for a test?
What is a power curve and how is it applicable to hypothesis testing?
10.78 Website administrators sometimes use analysis tools or service providers to “track” the movements of visitors to the various portions of their site. Overall, the administrator of a

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