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Business Statistics In Practice 6th Edition Bruce Bowerman, Richard O'Connell - Solutions

The following MINITAB output relates to a house having 2,000 square feet and a rating of 8.a. Report (as shown on the output) a point estimate of and a 95 percent confidence interval for the mean sales price of all houses having 2,000 square feet and a rating of 8.b. Report (as shown on the output)
Consider the demand for Fresh Detergent in a future sales period when Enterprise Industries' price for Fresh will be x1 = 3.70, the average price of competitors" similar detergents will be x2 = 3.90, and Enterprise Industries* advertising expenditure for Fresh will be x3 = 6.50. A 95 percent
Neter. Kutner, Nachtsheim, and Wasserman (1996) relate the speed, y, with which a particular insurance innovation is adopted to the size of the insurance firm, x, and the type of firm. The dependent variable y is measured by the number of months elapsed between the time the first firm adopted the
Consider the fuel consumption problem in which a natural gas company wishes to predict weekly fuel consumption for its city. In the exercises of Chapter 13, we used the single predictor variable x, average hourly temperature, to predict y, weekly fuel consumption. We now consider predicting y on
Table 3.12 gives the selling price (Price, expressed in thousands of dollars), the square footage (SqrFt), the number of bathrooms (Bathrms). and the niceness rating (Niceness, expressed as an integer from 1 to 7) of 80 homes randomly selected from all homes sold in a Florida city during the last
The Tastee Bakery Company supplies a bakery product to many supermarkets in a metropolitan area. The company wishes to study the effect of the height of the shelf display employed by the supermarkets on monthly sales, y (measured in cases of 10 units each), for this product. Shelf display height
Recall from Exercise 14.5 that Enterprise Industries has observed the historical data in Table 14.5 concerning y (demand for Fresh liquid laundry detergent), x1 (the price of Fresh), x2 (the average industry price of competitors' similar detergents), and x3 (Enterprise Industries' advertising
Figure 14.22 presents the Excel output of a regression analysis of the Fresh demand data using the modely = Î²0 + Î²1x1 + Î²2x2 + Î²3x3 + Î²4D4 + Î²5DC + Î²5DC + Î²6x3DB + Î²7x3DC + ÎµFIGURE 14.22Excel Output of a Regression Analysis of the Fresh Demand Data Using the Model y =
When we perform a partial F test, what are the complete and reduced models?
In Model 2, test H0: β4 = β5 = 0 by setting a equal to .05 and .01. Interpret your results.
In Model 3, test H0: β4 = β5 = β6 = β7 = 0 by setting α equal to .05 and .01. Interpret.
In Model 3, test H0: β6 = β7 = 0 by setting a equal to .05 and .01. Interpret your results.
Discuss how we use residual plots to check the regression assumptions for a multiple regression model.
A real estate agency collects the data in Table 14.4 concerningy = sales price of a house (in thousands of dollars)x1 = home size (in hundreds of square feet)x2 = rating (an overall "niceness rating" for the house expressed on a scale from l [worst] to l0 [best|, and provided by the real estate
Recall that Figure 13.26(a) gives n = 16 weekly values of Pages' Bookstore sales (y), Pages' advertising expenditure (x1), and competitor's advertising expenditure (x2). Use MINITAB or Excel, to fit the model y = β0 + β1x1 + β2x2 + ε and plot the model's residuals versus time. Does the residual
The trend in home building in recent years has been to emphasize open spaces and great rooms, rather than smaller living rooms and family rooms. A builder of speculative homes in the college community of Oxford, Ohio, had been building such homes, but his homes had been taking many months to sell
In the article "The Effect of Promotion Timing on Major League Baseball Attendance" (Sport Marketing Quarterly. December 1999), T. C. Boyd and T. C. Krehbiel use data from six major league baseball teams having outdoor stadiums to study the effect of promotion timing on major league baseball
Recall the Florida pool home case discussed in Exercise 14.30. Residual plots resulting from fitting the modelPrice = β0 + β1 SqrFt + β2 Bathrms + β3 Niceness + β4 Pool? + εare as shown in Figure 14.26 on the next page.a. The residuals are plotted against the predicted prices and against each
The personnel director of a firm has developed two tests to help determine whether potential employees would perform successfully in a particular position. To help estimate the usefulness of the tests, the director gives both tests to 43 employees who currently hold the position. Table 14.15 gives
Enterprise Industries produces Fresh, a brand of liquid laundry detergent. In order to manage its inventory more effectively and make revenue projections, the company would like to better predict demand for Fresh. To develop a prediction model, the company has gathered data concerning demand for
Table 14.6 presents data concerning the need for labor in 16 U.S. Navy hospitals. Here, y = monthly labor hours required; x1 = monthly X-ray exposures; x2 = monthly occupied bed days (a hospital has one occupied bed day if one bed is occupied for an entire day); and b3 = average length of patients'
a. What do R2 and 2 measure? b. How do R2 and 2 differ?
If we use the logistic regression modelto analyze the performance data in Table 15.5, we find that the point estimates of the model parameters and their associated p-values (given in parentheses) are b0 = -43.37(.00l) and b1 = .4897(.00l). Find a point estimate of the probability of success for a
Mendenhall and Sincich (1993) present data that can be used to investigate allegations of gender discrimination in the hiring practices of a particular firm. These data are as follows:In this table, y is a dummy variable that equals 1 if a potential employee was hired and 0 otherwise; x1 is the
What is multicollinearity? What problems can be caused by multicollinearity? Discuss.
Recall that Table 14.6 (page 590) presents data concerning the need for labor in 16 U.S. Navy hospitals. This table gives values of the dependent variable Hours (monthly labor hours) and of the independent variables Xray (monthly X-ray exposures), BedDays (monthly occupied bed days-a hospital has
In the quadratic regression model, what are y, (β0 + β1x + β2x2), and ε?
Use Figure 15.23(a) on page 669 to explain why Model I without hospital 14 has made the original hospital 17 considerably less influential and the original hospital 16 only slightly more influential.
Use Figure 15.23(b) on page 669 to explain why Model II has made hospital 17 considerably less influential, hospital 15 slightly more influential, and hospital 14 no longer an outlier with respect to its y value.
What is the purpose of a fractional power transformation?
Western Steakhouses, a fast-food chain, opened 15 years ago. Each year since then the number of steakhouses in operation, y, was recorded. An analyst for the firm wishes to use these data to predict the number of steakhouses that will be in operation next year. The data are given in Figure 15.30(a)
Figure 15.5 presents the MINITAB output of a regression analysis of the real estate sales price data (see the page margin) using the modely = Î²0 + Î²1x1 + Î²2x2 + Î²2x22 + eFIGURE 15.5MINITAB Output of a Regression Analysis of the Real Estate Sales Price Data Using the Model y = Î²0 +
A simple linear regression model is employed to analyze the 24 monthly observations given in Table 15.10 on the next page. Residuals are computed and are plotted versus time. The resulting residual plot is shown in Figure 15.37 on the next page. Discuss why the residual plot suggests the existence
Recall from Exercise 14.32 (page 616) that Enterprise Industries has advertised Fresh liquid laundry detergent by using three different advertising campaigns-advertising campaign A (television commercials), advertising campaign B (a balanced mixture of television and radio commercials) and
Consider the QHIC data in Figure 13.21 (page 556). When we performed a regression analysis of these data by using the simple linear regression model, plots of the model's residuals versus x (home value) and Å· (predicted upkeep expenditure) both fanned out and had a "dip." or slightly curved
How do home prices vary with square footage, age, and a variety of other factors? The Data and Story Library (DASL) contains data, including the sale price, for a random sample of 117 homes sold in Albuquerque, New Mexico. Go to the DASL website (lib.stat. cmu.edu/DASL/) and retrieve the home price
United Oil Company is attempting to develop a reasonably priced unleaded gasoline that will deliver higher gasoline mileages than can be achieved by its current unleaded gasolines. As part of its development process. United Oil wishes to study the effect of two independent variables-x1, amount of
We concluded in Exercise 15.3 that the modely = Î²0 + Î²1xl + Î²2x2 + Î²1x22 + Îµmight appropriately relate y to x1 and x2. To investigate whether interaction exists between x1 and x2, we consider the modely = Î²0 + Î²1xl
In this exercise we study the nature of the interaction between x1, square footage, and x2, rating.a. Consider all houses with a rating of 2. In this case, predicted sales price is (using the least squares point estimates in Figure 15.11)Calculate Å· when x1 = 13 and 22. Plot Å· versus x1, for
Compute a point forecast of tractor sales (based on trend and seasonal factors) for each of the quarters next year.
Compute an approximate 95 percent prediction interval forecast of tractor sales for each of the quarters next year. Use the fact that the half-lengths of 95 percent prediction intervals for the deseasonalized sales values in the four quarters of next year are. respectively, 14, 14.4, 14.6, and 15.
If we use the multiplicative decomposition method to analyze the quarterly bicycle sales data given in Table 16.3 (page 700). We find that the quarterly seasonal factors are .46, 1.22, 1.68. and .64. Furthermore, if we use a statistical software package to fit a straight line to the deseasonalized
Discuss the difference between constant seasonal variation and increasing seasonal variation.
Consider Figure 16.15(a) on page 721. Show how 2 and b2 have been calculated from 1, b1 and y2. Also, show how ŷ27(24) in Figure 16.15(b) has been calculated from 24 and b24.
Consider Figure 16.18(a) on page 726. Show how 35, b35, and sn35 have been calculated from 34, b34, y35, and sn23. Also, show how ŷ38(36) in Figure 16.18(b) has been calculated from 36, b36, and sn26.
Below we present new retail passenger car sales in the United States for each of the years 1990 to 1996:a. By using the year 1990 as the base year, construct a simple index for the passenger car sales data.b. Interpret the meaning of the index in each of the years 1993 and 1996.
In the following table we present the average prices of three precious metals-gold, silver, and platinum-for the years 1988 through 1996:a. By using the year 1988 as the base year, construct a simple index for each of gold, silver, and platinum.b. Using the three indexes you constructed in part a,
In the following table we present prices for three commonly used sources of energy-motor gasoline, natural gas, and electricity-for the years 1990 through 1996:a. Consider a family that consumes 1,850 gallons of gasoline, 150 mcf of natural gas, and 17.000 kilowatt-hours of electricity every year.
In this problem we consider annual U.S. lumber production over 30 years. The data were obtained from the U.S. Department of Commerce Survey of Current Business and are presented in Table 16.5a. Plot the lumber production values versus time and discuss why the plot indicates that the modelyt = β0 +
The State University Credit Union, a savings institution open to the faculty and staff of State University, handles savings accounts and makes loans to members. In order to plan its investment strategies, the credit union requires both point and prediction interval forecasts of monthly loan
Alluring Tackle, Inc.. a manufacturer of fishing equipment, makes the Bass Grabber, a type of fishing lure. The company would like to develop a prediction model that can be used to obtain point forecasts and prediction interval forecasts of the sales of the Bass Grabber. The sales (in tens of
The following table gives information concerning finance rates (in percent) for consumer installment loans from 1990 to 1996:a. Using 1990 as the base year, construct an aggregate index of finance rates charged by commercial banks.b. Using 1993 as the base year, construct an aggregate index of
ISO 9000 is a series of international standards for quality assurance management systems. Companies meeting the standards are considered to be "ISO 9000 registered." The periodical Business Standards maintains information about ISO 9000 registrations on its website (www.businessstandards.com). In
The past 20 monthly sales figures for a new type of watch sold at Lambert's Discount Stores are given in Table 16.6.a. Plot the watch sales values versus time and discuss why the plot indicates that the modelyt = β0 + β1t + ε1might appropriately describe these values.b. The least squares point
Bargain Department Stores, Inc., is a chain of department stores in the Midwest. Quarterly sales of the "Bargain 8(KK)-Btu Air Conditioner" over the past three years are as given in the left hand portion of Table 16.7 on the next page.TABLE 16.7Air Conditioner Salesa. Plot sales versus time and
What transformations can be used to transform a time series exhibiting increasing seasonal variation into a time series exhibiting constant seasonal variation?
Table 16.8 gives the monthly international passenger totals over the last 11 years for an airline company. A plot of these passenger totals reveals an upward trend with increasing seasonal variation, and the natural logarithmic transformation is found to best equalize the seasonal variation [see
In the book Tools and Methods for the Improvement of Quality, Gitlow, Gitlow. Oppenheim. and Oppenheim discuss a resort hotel's efforts to improve service by reducing variation in the time it takes to clean and prepare rooms. In order to study the situation, five rooms are selected each day for 25
A pizza restaurant monitors the size (measured by the diameter) of the 10-inch pizzas that it prepares. Pizza crusts are made from doughs that are prepared and prepackaged in boxes of 15 by a supplier. Doughs are thawed and pressed in a pressing machine. The toppings are added, and the pizzas are
A chemical company has collected 15 daily subgroups of measurements of an important chemical property called "acid value" for one of its products. Each subgroup consists of six acid value readings: a single reading was taken every four hours during the day, and the readings for a day are taken as a
The data in Table 17.9 consist of 30 subgroups of measurements that specify the location of a "tube hole" in an air conditioner compressor shell. Each subgroup contains the tube hole dimension measurement for five consecutive compressor shells selected from the production line. The first 15
a. Calculate appropriate revised x and R chart control limits.b. When the remaining 16's and 16 R's are plotted with respect to the appropriate revised control limits, they are found to be within these limits. What does this imply?
In the book Tools and Methods for the Improvement of Quality, Gitlow, Gitlow, Oppenheim, and Oppenheim discuss an example of using x̅ and R charts to study tuning knob diameters. In their problem description the authors say this:A manufacturer of high-end audio components buys metal tuning knobs
In the June 1991 issue of Quality Progress, Gunter presents several control charts. Four of these charts are reproduced in Figure 17.18. For each chart, tind any evidence of a lack of statistical control (that is, for each chart identify any evidence of the existence of one or more assignable
In the book Tools and Methods for the Improvement of Quality, Gitlow. Gitlow. Oppenheim. and Oppenheim present several control charts in a discussion and exercises dealing with pattern analysis. These control charts, which include appropriate A, B, and C zones, are reproduced in Figure 17.19. For
a. Calculate all of the zone boundaries for the chart.b. Calculate all of the R chart zone boundaries that are either 0 or positive.
a. Assuming that the cleaning and preparation times are approximately normally distributed, calculate a range of values that contains almost all (approximately 99.73 percent) of the individual cleaning and preparation times.b. Find reasonable estimates of the maximum and minimum times needed to
a. Compute the natural tolerance limits (limits that contain almost all the individual moisture content readings) for this process.b. If moisture content specifications are 6.0 percent ±.5 percent, is this process capable of meeting the specifications? Why or why not?c. Estimate the fraction of
a. Calculate a range of values that contains almost all (approximately 99.73 percent) of the individual grapefruit weights.b. Find a reasonable estimate of the maximum weight of a grapefruit that the grocer is likely to sell.c. Suppose that the grocer's contract with its produce supplier specifies
Consider the pizza crust diameters for 10-inch pizzas given Exercise 17.11 (pages 768-769).We found that, by removing an assignable cause, we were able to bring the process into statistical control with x̅̅ = 10.2225 and = .825.a. Recalling that the subgroup size for the pizza crust x
a. Recalling that the fill weight and R charts are based on subgroups of size 5, and assuming that the fill weights are approximately normally distributed, calculate the natural tolerance limits for the process.b. Suppose that management wishes to reduce the mean fill weight in order to save money
Suppose that = .I and n = 100. Calculate the upper and lower control limits, UCL and LCL, of the corresponding p chart.
Suppose that = .04 and n = 400. Calculate the upper and lower control limits, UCL and LCL, of the corresponding p chart.
In the July 1989 issue of Quality Progress. William J. McCabe discusses using a p chart to study a company's order entry system. The company was experiencing problems meeting the promised 60-day delivery schedule. An investigation found that the order entry system frequently lacked all the
In the book Tools and Methods for the Improvement of Quality, Gitlow, Gitlow, Oppenheim, and Oppenheim discuss a data entry operation that makes a large number of entries every day. Over a 24-day period, daily samples of 200 data entries are inspected. Table 17.12 gives the number of erroneous
In the July 1989 issue of Quality Progress, William J. McCabe discusses using a p chart to study the percentage of errors made by 21 buyers processing purchase requisitions. The p chart presented by McCabe is shown in Figure 17.26. In his explanation of this chart, McCabe says,The causes of the
The customer service manager of a discount store monitors customer complaints. Each day a random sample of 100 customer transactions is selected. These transactions are monitored, and the number of complaints received concerning these transactions during the next 30 days is recorded. The numbers of
Using the data in Table 17.13:a. Calculate x̅̅ and and then find the center lines and control limits for x̅ and R charts for the camshaft hardness depths.b. Set up the x̅ and R charts for the camshaft hardness depth data.c. Are the x̅ and R charts in statistical control? Explain.
a. Calculate the control limits for the chart in Figure 17.34.b. Calculate the upper control limit for the R chart in Figure 17.34.c. Are the and R charts for the 30 new subgroups using Coil #2 (which we recall was of the same type as Coil #1) in statistical control? Explain.
Consider the x and R charts in Figure 17.34.a. Calculate the natural tolerance limits for the improved process.b. Recalling that specifications state that the hardness depth of each camshaft must be between 3.0 mm. and 6.0 mm., is the improved process capable of meeting these specifications?
a. Calculate the control limits for the and R charts in Figure 17.35.b. Is the process (using the redesigned coil) in statistical control? Explain.c. Calculate the natural tolerance limits for the process (using the redesigned coil).d. Is the process (using the redesigned coil) capable of meeting
A bank officer wishes to study how many credit cardholders attempt to exceed their established credit limits. To accomplish this, the officer randomly selects a weekly sample of 100 of the cardholders who have been issued credit cards by the bank, and the number of cardholders who have attempted to
Explain why a change in process variability shows up on both the and R charts.
Table 17.5 gives five subgroups of measurement data. Use these data toa. Find x̅ and R for each subgroup.b. Find x̅̅ and R̅.c. Find A2 and D4.d. Compute x̅ and R chart center lines and control limits.
A loan officer at a bank wishes to compare the mortgage rates charged at banks in Texas with the mortgage rates of Texas savings and loans. Two independent random samples of bank mortgage rates and savings and loan mortgage rates in Texas are obtained with the following results:Because both samples
A company collected employee absenteeism data (in hours per year) at two of its manufacturing plants. The data were obtained by randomly selecting a sample from all of the employees at the first plant, and by randomly selecting another independent sample from all of the employees at the second
The following table presents samples of hourly yields for catalysts XA-100 and ZB-200. We analyzed these data using a two independent sample t test in Example 10.4 (page 405).Catalyst XA-100Catalyst
Recall that in Exercise 10.31 (page 416) we compared 30-year and 15-year fixed rate mortgage loans for a number of Willamette Valley lending institutions. The results obtained are shown in Table 18.4. Use the Wilcoxon signed ranks test and the following MINITAB output to determine whether, for
A consumer advocacy group is concerned about the ability of tax preparation firms to correctly prepare complex returns. To test the performance of tax preparers in two different tax preparation firms-Quick Tax and Discount Tax-the group designed ten tax cases for families with gross annual incomes
A human resources director wishes to assess the benefits of sending a company's managers to an innovative management course. Twelve of the company's managers are randomly selected to attend the course, and a psychologist interviews each participating manager before and after taking the course.
Recall that in Exercise 10.32 (page 417) we compared preexposure and postexposure attitude scores for an advertising study by using a paired difference / test. The data obtained and related Excel add-in (MegaStat) output are shown in Table 18.6 on the next page. Use the Wilcoxon signed ranks test
Use the Kruskal-Wallis H test to compare display panels A, B. and C using the data in Table 18.8. Use Î± = .05.TABLE 18.8Display Panel Study Data (Time, in Seconds, Required to Stabilize Air Traffic Emergency Condition)
Use the Kruskal-Wallis H test to compare bottle designs A, B, and C using the data in Table 18.9. Use Î± = .01.TABLE 18.9Bottle Design Study Data (Sales during a 24-Hour Period)
Use the Kruskal-Wallis H test and the MINITAB output in Figure 18.5 to compare the bottom (B), middle (M), and top (T) display heights using the data in Table 18.10. Use Î± = .05. Then, repeat the analysis if the first sales value for the middle display height is found to be incorrect and must be
Use the Kruskal-Wallis H test to compare golf ball brands Alpha. Best. Century, and Divot using the data in Table 18.11. Use Î± = .01 and the Excel add-in (MegaStat) output on the right side of Table 18.11.TABLE 18.11Golf Ball Durability Test Results
Write the formula that we use to compute Spearman's rank correlation coefficient whena. There are no (or few) ties in the ranks of the x and y values.b. There are many ties in the ranks of the x and y values.
A sales manager ranks 10 people at the end of their training on the basis of their sales potential. A year later, the number of units sold by each person is determined. The following data and MegaStat output are obtained. Note that the manager's ranking of l is "best."a. Find rs on the Excel add-in
Compute rs and test H0: ps = 0 versus Ha: ps > 0 for the direct labor cost data below.
Again consider the price comparison situation in which weekly expenses were compared at two chains-Miller's and Albert's. Recall that independent random samples at the two chains yielded the following weekly expenses:Since the sample sizes are small, there might be reason to doubt that the
A drug company wishes to compare the effects of three different drugs (X, Y, and Z) that are being developed to reduce cholesterol levels. Each drug is administered to six patients at the recommended dosage for six months. At the end of this period the reduction in cholesterol level is recorded for

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