The data contained in the file CrudeCost shows the U.S. refiner acquisition cost of crude oil in dollars per barrel (Energy Information Administration website). a. Construct a time series plot. What type of pattern exists in the data? b. Compute the linear trend equation for the time series. Use the linear trend equation to forecast the crude cost for time period 49. c. Compute the quadratic trend equation for the time series. Use the quadratic trend equation to forecast the crude cost for period 49. d. Using MSE, which approach provides the most accurate forecasts for the historical data?
> A simple random sample of 60 items resulted in a sample mean of 80. The population standard deviation is σ = 15. a. Compute the 95% confidence interval for the population mean. b. Assume that the same sample mean was obtained from a sample of 120 items
> A simple random sample of 50 items from a population with σ = 6 resulted in a sample mean of 32. a. Provide a 90% confidence interval for the population mean. b. Provide a 95% confidence interval for the population mean. c. Provide a 99% confidence in
> A simple random sample of 40 items resulted in a sample mean of 25. The population standard deviation is σ = 5. a. What is the standard error of the mean, σx? b. At 95% confidence, what is the margin of error?
> An investor wants to select one of seven mutual funds for the coming year. Data showing the percentage annual return for each fund during five typical one-year periods are shown here. The assumption is that one of these five-year periods will occur again
> Many factors influence the retail price of gasoline. The following table shows the average retail price for a gallon of regular grade gasoline for each year from 2014 through 2017 (U.S. Energy Information Administration website). Year Average …………………………
> Samples of size 5 provided the following 20 sample means for a production process that is believed to be in control. a. Based on these data, what is an estimate of the mean when the process is in control? b. Assume that the process standard deviation i
> A manufacturer produces lots of a canned food product. Let p denote the proportion of the lots that do not meet the product quality specifications. An η = 25, c = 0 acceptance sampling plan will be used. a. Compute points on the operating characteristic
> An acceptance sampling plan with n = 15 and c = 1 has been designed with a producer’s risk of .075. a. Was the value of p0 .01, .02, .03, .04, or .05? What does this value mean? b. What is the consumer’s risk associated with this plan if p1 is .25?
> An n = 10, c = 2 acceptance sampling plan is being considered; assume that p0 = .05 and p1 = .20. a. Compute both producer’s and consumer’s risk for this acceptance sampling plan. b. Would the producer, the consumer, or both be unhappy with the proposed
> According to the IRS, taxpayers calling the IRS in 2017 waited 13 minutes on average for an IRS telephone assister to answer. Do callers who use the IRS help line early in the day have a shorter wait? Suppose a sample of 50 callers who placed their calls
> Managers of 1200 different retail outlets make twice-a-month restocking orders from a central warehouse. Past experience shows that 4% of the orders result in one or more errors such as wrong item shipped, wrong quantity shipped, and item requested but n
> An insurance company samples claim forms for errors created by its employees as well as the amount of time it takes to process a claim. a. When the process is in control, the proportion of claims with an error is .033. A p chart has LCL = 0 and UCL = .06
> The following were collected for the Master Blend Coffee production process. The data show the filling weights based on samples of 3-pound cans of coffee. Use these data to construct the xÌ… and R charts. What conclusions can be made about th
> The following are quality control data for a manufacturing process at Kensport Chemical Company. The data show the temperature in degrees centigrade at five points in time during a manufacturing cycle. The company is interested in using control charts to
> Twenty-five samples of size 5 resulted in x̅ = 5.42 and R̅ = 2.0. Compute control limits for the x̅ and R charts, and estimate the standard deviation of the process.
> Product filling weights are normally distributed with a mean of 350 grams and a standard deviation of 15 grams. a. Develop the control limits for the x chart for samples of size 10, 20, and 30. b. What happens to the control limits as the sample size is
> Williams Sonoma is a consumer retail company that sells kitchenware. Williams Sonoma has reported the quantity and product value information for three different glass tumblers in two different years in the table that follows. Compute a weighted aggregate
> The closing price of Walmart stock at the end of its fiscal year (end of January) for five years is given in the following table. The CPI for January of each year is also provided. Deflate the stock price series and comment on the financial performance o
> Actuaries are analysts who specialize in the mathematics of risk. Actuaries often work for insurance companies and are responsible for setting premiums for insurance policies. Below are the median salaries for actuaries and the yearly CPI for four years.
> The operations of seafood restaurant chains such as Red Lobster are sensitive to changes in the price of seafood. Quantity data for a regional seafood chain coupled with price data are in the following table (Statista website). a. Compute a price rela
> The American Institute of Certified Tax Planners reports that the average U.S. CPA works 60 hours per week during tax season. Do CPAs in states that have flat state income tax rates work fewer hours per week during tax season? Conduct a hypothesis test t
> Compute the price relatives for the four stocks making up the Boran index in exercise 20. Use the weighted aggregates of price relatives to compute the January of Year 3 and March of Year 3 Boran indexes. Exercise 20: Boran Stockbrokers, Inc., selects f
> Boran Stockbrokers, Inc., selects four stocks for the purpose of developing its own index of stock market behavior. Prices per share for a Year 1 base period, January of Year 3, and March of Year 3 follow. Base-year quantities are set on the basis of his
> Use the price data in exercise 18 to compute a Paasche index for the shipping cost if Year 5 quantities are 4000, 3000, 7500, and 3000 for the four products, respectively. Exercise 18: Nickerson Manufacturing Company has the following data on quantities
> Nickerson Manufacturing Company has the following data on quantities shipped and unit shipping costs for each of its four products: a. Compute the price relative for each product. b. Compute a weighted aggregate price index that reflects the shipping c
> Nielsen Research provides weekly ratings of nationally broadcast television programs. The mean weekly number of viewers for the 207 prime-time programs broadcast by five major televisions networks (ABC, CBS, FOX, NBC, and CW) for the 2017â€
> A sample of 15 students received the following rankings on midterm and final examinations in a statistics course. Compute the Spearman rank-correlation coefficient for the data and test for a significant correlation with α = .10. What is th
> Course evaluation ratings for four college instructors are shown in the following table. Use α = .05 and test for a significant difference among the rating for these instructors. What is your conclusion?
> A sample of 20 engineers employed with a company for three years has been rank ordered with respect to managerial potential. Some of the engineers attended the company’s management-development course, others attended an off-site managem
> A client wants to determine whether there is a significant difference in the time required to complete a program evaluation with the three different methods that are in common use. The times (in hours) required for each of 18 evaluators to conduct a prog
> The following data are product weights for the same items produced on two different production lines. Test for a difference between the product weights for the two lines. Use α = .05. Line 1 …………………………………………… Line 2 13.6 …………………………………………………. 13.7 13.8 …
> TextRequest reports that adults 18–24 years old send and receive 128 texts every day. Suppose we take a sample of 25–34 year olds to see if their mean number of daily texts differs from the mean for 18–24 year olds reported by TextRequest. a. State the n
> A study was designed to evaluate the weight-gain potential of a new poultry feed. A sample of 12 chickens was used in a six-week study. The weight of each chicken was recorded before and after the six-week test period. The differences between the before
> Twelve homemakers were asked to estimate the retail selling price of two models of refrigerators. Their estimates of selling price are shown in the following table. Use these data and test at the .05 level of significance to determine whether there is a
> According to the National Association of Realtors website (https://www.nar.realtor/sites/default/files/documents/metro-home-prices-q3-2017-single-family-2017-11-02.pdf), the national median sales price for single-family homes was $254,000 in 2018. Assume
> A survey asked the following question: Do you favor or oppose providing tax-funded vouchers or tax deductions to parents who send their children to private schools? Of the 2010 individuals surveyed, 905 favored the proposal, 1045 opposed the proposal, an
> Refer to the Hudson Marine data in exercise 53. a. Deseasonalize the data and use the deseasonalized time series to identify the trend. b. Use the results of part (a) to develop a quarterly forecast for next year based on trend. c. Use the seasonal index
> Refer to the Hudson Marine problem in exercise 53. a. Compute the centered moving average values for this time series. b. Construct a time series plot that also shows the centered moving average and original time series on the same graph. Discuss the dif
> Refer to the Hudson Marine problem in exercise 52. Suppose the quarterly sales values for the seven years of historical data are as follows. a. Use the following dummy variables to develop an estimated regression equation to account for any season and
> Hudson Marine provides boat sales, service, and maintenance. Boat trailers are one of its top sales items. The following table reports the number of trailers sold for the last seven years. a. Construct a time series plot. Does a linear trend appear to
> Refer to the Costello Music Company time series in exercise 49. a. Deseasonalize the data and use the deseasonalized time series to identify the trend. b. Use the results of part (a) to develop a quarterly forecast for next year based on trend. c. Use th
> Refer to the Costello Music Company problem in exercise 49. a. Using time series decomposition, compute the seasonal indexes for the four quarters. b. When does Costello Music experience the largest seasonal effect? Does this result appear reasonable? Ex
> In a study entitled How Undergraduate Students Use Credit Cards, it was reported that undergraduate students have a mean credit card balance of $3173. This figure was an all-time high and had increased 44% over the previous five years. Assume that a curr
> A sample containing years to maturity and yield for 40 corporate bonds are contained in the file CorporateBonds. a. What is the sample mean years to maturity for corporate bonds and what is the sample standard deviation? b. Develop a 95% confidence inter
> Consider the Costello Music Company problem in exercise 48. The quarterly sales data follow. a. Use the following dummy variables to develop an estimated regression equation to account for any seasonal and linear trend effects in the data: Qtr1 = 1 if
> The Costello Music Company has been in business for five years. During that time, sales of pianos increased from 12 units in the first year to 76 units in the most recent year. Fred Costello, the firm’s owner, wants to develop a forecas
> The following data show the price in dollars for a general admission ticket to the Magic Kingdom at Disney World from the year 2000 (period 1) to 2017 (period 18) (Travel 1 Leisure website). These data are in the file DisneyPrices. a. Construct a time-
> The Mayfair Department Store in Davenport, Iowa, is trying to determine the amount of sales lost while it was shut down during July and August because of damage caused by the Mississippi River flood. Sales data for January through June follow. a. Use
> Annual retail store revenue for Apple from 2007 to 2017 are shown below (investorapple website). a. Construct a time series plot. What type of pattern exists in the data? b. Using statistical software, develop a linear trend equation for this time seri
> United Dairies, Inc., supplies milk to several independent grocers throughout Dade County, Florida. Managers at United Dairies want to develop a forecast of the number of half-gallons of milk sold per week. Sales data for the past 12 weeks follow. a. C
> The following table reports the percentage of stocks in a portfolio for nine quarters. Quarter …………………………………………………… Stock % 1st—Year 1 …………………………………………………… 29.8 2nd—Year 1 …………………………………………………… 31.0 3rd—Year 1 …………………………………………………… 29.9 4th—Year 1 …………………
> The weekly demand (in cases) for a particular brand of automatic dishwasher detergent for a chain of grocery stores located in Columbus, Ohio, follows. a. Construct a time series plot. What type of pattern exists in the data? b. Use a three-week moving
> A study was conducted to investigate browsing activity by shoppers. Shoppers were classified as nonbrowsers, light browsers, and heavy browsers. For each shopper in the study, a measure was obtained to determine how comfortable the shopper was in the sto
> According to the IRS, individuals filing federal income tax returns prior to March 31 received an average refund of $1056 in 2018. Consider the population of “last-minute” filers who mail their tax return during the last five days of the income tax perio
> The U.S. Department of Energy’s Fuel Economy Guide provides fuel efficiency data for cars and trucks (www.fueleconomy.gov). The file FuelEconomy2019 provides a portion of the data for 387 vehicles from the 2019 model year. The column labeled Class identi
> Refer to the data in exercise 31. a. Develop an estimated regression equation that can be used to predict Delay by using Industry and Quality. b. Plot the residuals obtained from the estimated regression equation developed in part (a) as a function of t
> Refer to the data in exercise 31. Consider a model in which only Industry is used to predict Delay. At a .01 level of significance, test for any positive autocorrelation in the data. Exercise 31: In baseball, an earned run is any run the opposing team s
> A study investigated the relationship between audit delay (Delay), the length of time from a company’s fiscal year-end to the date of the auditor’s report, and variables that describe the client and the auditor. Some o
> In baseball, an earned run is any run the opposing team scores off a pitcher except for a run scored as a result of fielding errors. The earned run average (ERA) is a statistic commonly used to compare the performance of pitchers; the ERA of a pitcher is
> Consumer Reports tested 19 different brands and models of road, fitness, and comfort bikes. Road bikes are designed for long road trips; fitness bikes are designed for regular workouts or daily commutes; and comfort bikes are designed for leisure rides o
> A sample containing years to maturity and yield (%) CorporateBonds for 40 corporate bonds is contained in the file CorporateBonds (Barron’s). a. Develop a scatter diagram of the data using x = years to maturity as the independent variable. Does a simple
> For the holiday season of 2017, nearly 59 percent of consumers planned to buy gift cards. According to the National Retail Federation, millennials like to purchase gift cards (Dayton Daily News website). Consider the sample data in the file GiftCards. Th
> A portion of a data set containing information for 45 mutual funds that are part of the Morningstar Funds 500 follows. The complete data set is available in the file named MutualFunds. The data set includes the following five variables: Fund Type: The ty
> The Cincinnati Zoo and Botanical Gardens had a record attendance of 1.87 million visitors in 2017 (Cincinnati Business Courier website). Nonprofit organizations such as zoos and museums are becoming more sophisticated in their use of data to improve the
> Consider the following hypothesis test: H0: µ = 22 Ha: µ ≠ 22 A sample of 75 is used and the population standard deviation is 10. Compute the p-value and state your conclusion for each of the following sample results. Use α = .01. a. x̅ = 23 b. x̅ = 25.1
> The Tire Rack, America’s leading online distributor of tires and wheels, conducts extensive testing to provide customers with products that are right for their vehicle, driving style, and driving conditions. In addition, the Tire Rack m
> Recall that in exercise 50 the personnel director for Electronics Associates developed the following estimated regression equation relating an employee’s score on a job satisfaction test to length of service and wage rate. yÌ
> Recall that in exercise 49, the admissions officer for Clearwater College developed the following estimated regression equation relating final college GPA to the student’s SAT mathematics score and high-school GPA. ŷ = 21.
> A partial computer output from a regression analysis follows. a. Compute the missing entries in this output. b. Use the F test and α = .05 to see whether a significant relationship is present. c. Use the t test and α = .05 t
> The personnel director for Electronics Associates developed the following estimated regression equation relating an employee’s score on a job satisfaction test to his or her length of service and wage rate. ŷ= 14.4 - 8.69x1 + 13.5x2 where x1 = length of
> The admissions officer for Clearwater College developed the following estimated regression equation relating the final college GPA to the student’s SAT mathematics score and high-school GPA. ŷ = 21.41 + .0235x1 + .00486x2 where x1 = high-school grade po
> The Toyota Camry is one of the best-selling cars in North America. The cost of a previously owned Camry depends upon many factors, including the model year, mileage, and condition. To investigate the relationship between the car’s mileage and the sales p
> The Transactional Records Access Clearinghouse at Syracuse University reported data showing the odds of an Internal Revenue Service audit. The following table shows the average adjusted gross income reported and the percent of the returns that were audit
> Market betas for individual stocks are determined by simple linear regression. For each stock, the dependent variable is its quarterly percentage return (capital appreciation plus dividends) minus the percentage return that could be obtained from a risk-
> A marketing professor at Givens College is interested in the relationship between hours spent studying and total points earned in a course. Data collected on 10 students who took the course last quarter follow. Hours Spent Studying ……………………………. Total Po
> Consider the following hypothesis test: H0: µ ≤ 50 Ha: µ > 50 A sample of 60 is used and the population standard deviation is 8. Use the critical value approach to state your conclusion for each of the following sample results. Use α = .05. a. x̅ = 52.5
> The regional transit authority for a major metropolitan area wants to determine whether there is any relationship between the age of a bus and the annual maintenance cost. A sample of 10 buses resulted in the following data. Age of Bus (years) ………………… M
> A sociologist was hired by a large city hospital to investigate the relationship between the number of unauthorized days that employees are absent per year and the distance (miles) between home and work for the employees. A sample of 10 employees was cho
> In a manufacturing process the assembly line speed (feet per minute) was thought to affect the number of defective parts found during the inspection process. To test this theory, managers devised a situation in which the same batch of parts was inspected
> Jensen Tire & Auto is in the process of deciding whether to purchase a maintenance contract for its new computer wheel alignment and balancing machine. Managers feel that maintenance expense should be related to usage, and they collected the following in
> Is the number of square feet of living space a good predictor of a house’s selling price? The following data collected in April, 2015, show the square footage and selling price for fifteen houses in Winston Salem, North Carolina (Zillow.com). Size (1000
> The Dow Jones Industrial Average (DJIA) and the Standard & Poor’s 500 (S&P 500) indexes are used as measures of overall movement in the stock market. The DJIA is based on the price movements of 30 large companies; the S&P 50
> What is the purpose of testing whether β1 = 0? If we reject β2 = 0, does it imply a good fit?
> In your own words, explain the difference between an interval estimate of the mean value of y for a given x and an interval estimate for an individual value of y for a given x.
> Does a high value of r2 imply that two variables are causally related? Explain.
> Consider the following hypothesis test: H0: µ ≥ 80 Ha: µ < 80 A sample of 100 is used and the population standard deviation is 12. Compute the p-value and state your conclusion for each of the following sample results. Use α = .01. a. x̅ = 78.5 b. x̅ = 7
> A manufacturing company designed a factorial experiment to determine whether the number of defective parts produced by two machines differed and if the number of defective parts produced also depended on whether the raw material needed by each machine wa
> A factorial experiment was designed to test for any significant differences in the time needed to translate other languages into English with two computerized language translators. Because the type of language translated was also considered a significant
> A major manufacturer of golf equipment is considering three designs for a new driver: Design A, Design B, and Design C. Each design differs slightly in terms of the material used to construct the driver’s head and shaft. The company wou
> Jimmy Kimmel Live! on ABC, The Tonight Show Starring Jimmy Fallon on NBC, and The Late Show with Stephen Colbert on CBS are three popular late-night talk shows. The following table shows the number of viewers in millions for a 10-week period during the s
> A research firm tests the miles-per-gallon characteristics of three brands of gasoline. Because of different gasoline performance characteristics in different brands of automobiles, five brands of automobiles are selected and treated as blocks in the exp
> A Pew Research study conducted in 2017 found that approximately 75% of Americans believe that robots and computers might one day do many of the jobs currently done by people (Pew Research website, http://www.pewinternet.org/2017/10/04/americans-attitudes
> Three different assembly methods have been proposed for a new product. A completely randomized experimental design was chosen to determine which assembly method results in the greatest number of parts produced per hour, and 30 workers were randomly selec
> The following data show the percentage of 17- to 24-year-olds who are attending college in several metropolitan statistical areas in four geographic regions of the United States (U.S. Census Bureau website, https://www .census.gov/data.html). // Use α
> The U.S. Environmental Protection Agency (EPA) monitors levels of pollutants in the air for cities across the country. Ozone pollution levels are measured using a 500-point scale; lower scores indicate little health risk, and higher scores indicate great
> A study reported in the Journal of Small Business Management concluded that self-employed individuals do not experience higher job satisfaction than individuals who are not self-employed. In this study, job satisfaction is measured using 18 items, each o
> Consider the following hypothesis test: H0: µ = 15 Ha: µ ≠ 15 A sample of 50 provided a sample mean of 14.15. The population standard deviation is 3. a. Compute the value of the test statistic. b. What is the p-value? c. At α = .05, what is your conclusi
> In a completely randomized experimental design, three brands of paper towels were tested for their ability to absorb water. Equal-size towels were used, with four sections of towels tested per brand. The absorbency rating data follow. At a .05 level of s
> The Harris Poll tracks the favorite sport of Americans who follow at least one sport. Results of the poll show that professional football is the favorite sport of 33% of Americans who follow at least one sport, followed by baseball at 15%, menâ
> A Financial Times/Harris Poll surveyed people in six countries to assess attitudes toward a variety of alternate forms of energy. The data in the following table are a portion of the poll’s findings concerning whether people favor or op
