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business
business statistics for contemporary

Questions and Answers of Business Statistics For Contemporary

61. Health insurance. Based on a 2007 survey of U.S.households (see www.census.gov), 87% (out of 3060) of males in Massachusetts (MA) have health insurance.a) Examine the conditions for constructing
62. Health insurance, part 2. Using the same survey and data as in Exercise 61, we find that 84% of those respondents in Massachusetts who identified themselves as Black/African-Americans (out of
1. From Chapter 5 a survey of 25 randomly selected customers found the following ages (in years):Recall that the mean was 31.84 years and the standard deviation was 9.84 years.a) What is the standard
2. From Chapter 5, a random sample of 20 purchases showed the following amounts (in $):Recall that the mean was $45.26 and the standard deviation was $20.67.a) What is the standard error of the
5. Find the critical value for:a) a 95% confidence interval based on 24 df.b) a 95% confidence interval based on 99 df.
6. Find the critical value for:a) a 90% confidence interval based on 19 df.b) a 90% confidence interval based on 4 df.
10. For confidence intervals of Exercise 8, a histogram of the data looks like this:Check the assumptions and conditions for your inference. Number of Purchases 2 4 6 8 40 Amount ($) 80 90
11. For the confidence interval in Exercise 7:a) How large would the sample size have to be to cut the margin of error in half?b) About how large would the sample size have to be to cut the margin of
12. For the confidence interval in Exercise 8:a) To reduce the margin of error to about $4, how large would the sample size have to be?b) How large would the sample size have to be to reduce the
13. t-models. Using the t tables, software, or a calculator, estimate:a) the critical value of t for a 90% confidence interval withb) the critical value of t for a 98% confidence interval with
14. t-models, part 2. Using the t tables, software, or a calculator, estimate:a) the critical value of t for a 95% confidence interval withb) the critical value of t for a 99% confidence interval with
15. Confidence intervals. Describe how the width of a 95%confidence interval for a mean changes as the standard deviation(s) of a sample increases, assuming sample size remains the same.
16. Confidence intervals, part 2. Describe how the width of a 95% confidence interval for a mean changes as the sample size (n) increases, assuming the standard deviation remains the same.
17. Confidence intervals and sample size. A confidence interval for the price of gasoline from a random sample of 30 gas stations in a region gives the following statistics:a) Find a 95% confidence
18. Confidence intervals and sample size, part 2. A confidence interval for the price of gasoline from a random sample of 30 gas stations in a region gives the following statistics:a) Find a 95%
19. Marketing livestock feed. A feed supply company has developed a special feed supplement to see if it will promote y = $4.49 SE1y2 = $0.06 y = $4.49 s = $0.29 df = 102.df = 7.df = 88.df =
21. CEO compensation. A sample of 20 CEOs from the Forbes 500 shows total annual compensations ranging from a minimum of $0.1 to $62.24 million. The average for these 20 CEOs is $7.946 million. The
22. Credit card charges. A credit card company takes a random sample of 100 cardholders to see how much they charged on their card last month. A histogram and boxplot are as follows:A computer
24. Housing 2008 was a difficult year for the economy.There were a large number of foreclosures of family homes.In one large community, realtors randomly sampled 36 bids from potential buyers to
25. Parking, part 2. Suppose that for budget planning purposes the city in Exercise 23 needs a better estimate of the mean daily income from parking fees.a) Someone suggests that the city use its
26. Housing, part 2. In Exercise 24, we found a 95% confidence interval to estimate the loss in home values.a) Suppose the standard deviation of the losses was $3000 instead of the $1500 used for
27. State budgets. States that rely on sales tax for revenue to fund education, public safety, and other programs often end up with budget surpluses during economic growth periods(when people spend
28. State budgets, part 2. Suppose the state in Exercise 27 sampled 16 small retailers instead of 51, and for the sample of 16, the sample mean increase again equaled $2350 in additional sales tax
29. Departures. What are the chances your flight will leave on time? The U.S. Bureau of Transportation Statistics of the Department of Transportation publishes information about airline performance.
30. Late arrivals. Will your flight get you to your destination on time? The U.S. Bureau of Transportation Statistics reported the percentage of flights that were late each month from 1995 through
31. Computer lab fees. The technology committee has stated that the average time spent by students per lab visit has increased, and the increase supports the need for increased lab fees. To
32. Cell phone batteries. A company that produces cell phones claims its standard phone battery lasts longer on average than other batteries in the market. To support this claim, the company
33. Growth and air pollution. Government officials have difficulty attracting new business to communities with troubled reputations. Nevada has been one of the fastest growing states in the country
34. Convention revenues. At one time, Nevada was the only U.S. state that allowed gambling. Although gambling continues to be one of the major industries in Nevada, the proliferation of legalized
35. Traffic speed. Police departments often try to control traffic speed by placing speed-measuring machines on roads that tell motorists how fast they are driving. Traffic safety experts must
36. Traffic speed, part 2. The speed-measuring machines must measure accurately to maximize effectiveness in slowing traffic. The accuracy of the machines will be tested before placement on city
38. Tax audits, part 2. While reviewing the sample of audit fees, a senior accountant for the firm notes that the fee charged by the firm’s accountants depends on the complexity of the return. A
39. Wind power. Should you generate electricity with your own personal wind turbine? That depends on whether you have enough wind on your site. To produce enough energy, your site should have an
1. For each of the following situations, define the parameter(proportion or mean) and write the null and alternative hypotheses in terms of parameter values. Example: We want to know if the
7. For each of the following, write out the null and alternative hypothesis, being sure to state whether it is one-sided or two-sided.a) A company reports that last year 40% of their reports in
9. The owner of the store from Chapter 12, Exercise 1, wants to know if the mean age of all customers is 25 years old.a) What is the null hypothesis?b) Is the alternative one- or two-sided?c) What is
10. The analyst in Chapter 12, Exercise 2, wants to know if the mean purchase amount of all transactions is at least $40.a) What is the null hypothesis?b) Is the alternative one- or two-sided?c) What
13. For each of the following situations, find the critical value(s) for z or t.a) vs. atb) vs. atc) vs. atd) vs. ate) vs. at
14. For each of the following situations, find the critical value for z or t.a) vs. atb) vs. atc) vs. atd) vs. ate) vs. at
15. Suppose that you are testing the hypotheses 0.20 vs. A sample of size 250 results in a sample proportion of 0.25.a) Construct a 95% confidence interval for p.HA: p Z 0.20.H0: p =H0: p = 0.2 HA: p
16. Suppose that you are testing the hypotheses 0.40 vs. A sample of size 200 results in a sample proportion of 0.55.a) Construct a 90% confidence interval for p.b) Based on the confidence interval,
17. Suppose that you are testing the hypotheses 16 vs. A sample of size 25 results in a sample mean of 16.5 and a standard deviation of 2.0.a) What is the standard error of the mean?b) What is the
18. Suppose that you are testing the hypotheses 80 vs. A sample of size 61 results in a sample mean of 75 and a standard deviation of 1.5.a) What is the standard error of the mean?b) What is the
20. For each of the following situations, state whether a Type I, a Type II, or neither error has been made. a) A test of Ho: hypothesis. Later it is discovered that u = 24.9. 25 vs. HA: > 25 rejects
21. Hypotheses. Write the null and alternative hypotheses to test each of the following situations.a) An online clothing company is concerned about the timeliness of their deliveries. The VP of
22. More hypotheses. Write the null and alternative hypotheses to test each of the following situations.a) A business magazine article reports that, in 1990, 35%of CEOs had an MBA degree. Has the
23. Deliveries. The clothing company in Exercise 21a looks at a sample of delivery reports. They test the hypothesis that 90% of the deliveries are on time against the alternative that greater than
24. House sales. The realty company in Exercise 21b looks at a recent sample of houses that have sold. On testing the null hypothesis that 50% of the houses take more than three months to sell
25. P-value. Have harsher penalties and ad campaigns increased seat-belt use among drivers and passengers?Observations of commuter traffic have failed to find evidence of a significant change
26. Another P-value. A company developing scanners to search for hidden weapons at airports has concluded that a new device is significantly better than the current scanner.The company made this
27. Ad campaign. An information technology analyst believes that they are losing customers on their website who find the checkout and purchase system too complicated.She adds a one-click feature to
28. Mutual funds. A mutual fund manager claims that at least 70% of the stocks she selects will increase in price over the next year. We examined a sample of 200 of her selections over the past three
29. Product effectiveness. A pharmaceutical company’s old antacid formula provided relief for 70% of the people who used it. The company tests a new formula to see if it is better and gets a
30. Car sales. A German automobile company is counting on selling more cars to the younger market segment—drivers under the age of 20. The company’s market researchers survey to investigate
31. False claims? A candy company claims that in a large bag of holiday M&M’s® half the candies are red and half the candies are green. You pick candies at random from a bag and discover that of
33. E-commerce. A market researcher at a major clothing company that has traditionally relied on catalog mailorder sales decides to investigate whether the amount of online sales has changed. She
34. Performance standards. The United States Golf Association (USGA) sets performance standards for golf balls. For example, the initial velocity of the ball may not exceed 250 feet per second when
35. Social Security payments. The average monthly Social Security benefit for widows and widowers in 2005 was $967 (Statistical Abstract of the United States, U.S.Census Bureau). Payments vary from
36. Social Security payments, part 2. In a neighboring county, a newspaper wrote that widow/widower Social Security benefits were significantly lower in the county than in all the other counties of
37. Spike poll. In August 2004, Time magazine reported the results of a random telephone poll commissioned by the Spike network. Of the 1302 men who responded, only 39 said that their most important
38. Stocks. A young investor in the stock market is concerned that investing in the stock market is actually gambling, since the chance of the stock market going up on any given day is 50%. She
39. Economy. In 2008, a Gallup Poll asked 2336 U.S. adults, aged 18 or over, how they rated economic conditions. In a poll conducted from January 27 through February 1, 2008, 24% rated the economy as
40. Economy, part 2. The same Gallup Poll data from Exercise 39 also reported that 33% of those surveyed rated the economy as Poor. The same media outlet claimed the true proportion to be 30%. Does
41. Convenient alpha. An enthusiastic junior executive has run a test of his new marketing program. He reports that it resulted in a “significant” increase in sales. A footnote on his report
42. Safety. The manufacturer of a new sleeping pill suspects that it may increase the risk of sleepwalking, which could be dangerous. A test of the drug fails to reject the null hypothesis of
43. Product testing. Since many people have trouble programming their VCRs, an electronics company has developed what it hopes will be easier instructions.The goal is to have at least 96% of
44. Marketing. In November 2001, the Ag Globe Trotter newsletter reported that 90% of adults drink milk.A regional farmers organization planning a new marketing campaign across its multicounty area
45. E-commerce, part 2. The average age of online consumers a few years ago was 23.3 years. As older individuals gain confidence with the Internet, it is believed that the average age has increased.
46. Fuel economy. A company with a large fleet of cars hopes to keep gasoline costs down and sets a goal of attaining a fleet average of at least 26 miles per gallon. To see if the goal is being met,
47. Pricing for competitiveness. SLIX wax is developing a new high performance fluorocarbon wax for cross country ski racing designed to be used under a wide variety of conditions.In order to justify
49. Environment. In the 1980s, it was generally believed that congenital abnormalities affected about 5% of the nation’s children. Some people believe that the increase in the number of chemicals
50. Billing company. A billing company that collects bills for doctors’ offices in the area is concerned that the percentage of bills being paid by Medicare has risen.Historically, that percentage
51. Education. The National Center for Education Statistics monitors many aspects of elementary and secondary education nationwide. Their 1996 numbers are often used as a baseline to assess changes.
52. Consumer confidence. At various times in 2007, when asked if economic conditions were getter better or worse, consistently more than 20% of U.S. adults said better. On January 19–20, 2008, when
53. Retirement. A survey of 1000 workers indicated that approximately 520 have invested in an individual retirement account. National data suggests that 44% of workers invest in individual retirement
54. Customer satisfaction. A company hopes to improve customer satisfaction, setting as a goal no more than 5%negative comments. A random survey of 350 customers found only 10 with complaints.a)
55. Maintenance costs. A limousine company is concerned with increasing costs of maintaining their fleet of 150 cars.After testing, the company found that the emissions systems of 7 out of the 22
56. Damaged goods. An appliance manufacturer stockpiles washers and dryers in a large warehouse for shipment to retail stores. Sometimes in handling them the appliances get damaged. Even though the
57. WebZine. A magazine called WebZine is considering the launch of an online edition. The magazine plans to go ahead only if it’s convinced that more than 25%of current readers would subscribe.
58. Truth in advertising. A garden center wants to store leftover packets of vegetable seeds for sale the following spring, but the center is concerned that the seeds may not germinate at the same
59. Women executives. A company is criticized because only 13 of 43 people in executive-level positions are women. The company explains that although this proportion is lower than it might wish,
60. Jury. Census data for a certain county shows that 19% of the adult residents are Hispanic. Suppose 72 people are called for jury duty, and only 9 of them are Hispanic.Does this apparent
61. Nonprofit. A nonprofit company concerned with the school dropout rates in the United States has designed a tutoring program aimed at students between 16 to 18 years old. The National Center for
62. Real estate. A national real estate magazine advertised that 15% of first-time home buyers had a family income below $40,000. A national real estate firm believes this percentage is too low and
63. Public relations. According to the U.S. Department of Transportation (DOT), passengers filed more complaints about airline service in 2007 than in 2006.One airline’s public relations department
65. Business ethics. One study reports that 30% of newly hired MBAs are confronted with unethical business practices during their first year of employment. One business school dean wondered if her
66. Stocks, part 2. A young investor believes that he can beat the market by picking stocks that will increase in value.Assume that on average 50% of the stocks selected by a portfolio manager will
67. U.S. politics. The national elections in 2008 apparently drew more interest and debate among voters than prior U.S. elections. A national sample of 2020 U.S.adults, aged 18 and older, surveyed
68. iPod reliability. MacInTouch reported that several versions of the iPod reported failure rates of 20% or more.From a customer survey, the color iPod, first released in 2004, showed 64 failures
69. Testing cars. A clean air standard requires that vehicle exhaust emissions not exceed specified limits for various pollutants. Many states require that cars be tested annually to be sure they
70. Quality control. Production managers on an assembly line must monitor the output to be sure that the level of defective products remains small. They periodically inspect a random sample of the
71. Testing cars, again. As in Exercise 69, state regulators are checking up on repair shops to see if they are certifying vehicles that do not meet pollution standards.a) In this context, what is
72. Quality control, part 2. Consider again the task of the quality control inspectors in Exercise 70.a) In this context, what is meant by the power of the test the inspectors conduct?b) They are
73. Statistics software. A Statistics professor has observed that for several years about 13% of the students who initially enroll in his Introductory Statistics course withdraw before the end of the
74. Radio ads. A company is willing to renew its advertising contract with a local radio station only if the station can prove that more than 20% of the residents of the city have heard the ad and
75. Statistics software, part 2. Initially, 203 students signed up for the Statistics course in Exercise 73. They used the software suggested by the salesperson, and only 11 dropped out of the
76. Radio ads, part 2. The company in Exercise 74 contacts 600 people selected at random, and 133 can remember the ad.a) Should the company renew the contract? Support your recommendation with an
77. Investment. Investment style plays a role in constructing a mutual fund. Many individual stocks can be grouped into two distinct groups: Growth and Value. A Growth stock is one with high earning
78. Manufacturing. A tire manufacturer is considering a newly designed tread pattern for its all-weather tires. Tests have indicated that these tires will provide better gas mileage and longer tread
79. Collections. Credit card companies lose money on cardholders who fail to pay their minimum payments. They use a variety of methods to encourage their delinquent cardholders to pay their credit

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