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Question 1 10.6

a. y = 4 + x

a. y = 5 – 2x

b. y = –4 + 3x

c. y = –2x

d. y = x

e. y = .50 + 1.5x

Give the slope and y-intercept for each of the lines graphed

Question 2 10.19

Ranking driving performance of professional golfers. Refer to The Sport Journal(Winter 2007) study of a new method for ranking the total driving performance of golfers on the Professional Golf Association (PGA) tour,  Exercise 2.50  (p.  63 ). Recall that the method computes a driving performance index based on a golfer’s average driving distance (yards) and driving accuracy (percent of drives that land in the fairway). Data for the top 40 PGA golfers (as ranked by the new method) are saved in the PGADRIVER file. (The first five and last five observations are listed in the table.)

Rank	Player	Driving Distance (yards)	Driving Accuracy (%)	Driving Performance Index
1	Woods	316.1	54.6	3.58
2	Perry	304.7	63.4	3.48
3	Gutschewski	310.5	57.9	3.27
4	Wetterich	311.7	56.6	3.18
5	Hearn	295.2	68.5	2.82
⋮	⋮	⋮	⋮	⋮
36	Senden	291	66	1.31
37	Mickelson	300	58.7	1.30
38	Watney	298.9	59.4	1.26
39	Trahan	295.8	61.8	1.23
40	Pappas	309.4	50.6	1.17

Source: Wiseman, F., et al. “A new method for ranking total driving performance on the PGA Tour,” The Sport Journal, Vol. 10, No. 1, Winter 2007 (Table 2).

a. Write the equation of a straight-line model relating driving accuracy (y) to driving distance (x).

b. Fit the model, part a, to the data using simple linear regression. Give the least squares prediction equation.

c. Interpret the estimated y-intercept of the line.

d. Interpret the estimated slope of the line.

e. In  Exercise 2.126  (p.  95 ), you were informed that a professional golfer, practicing a new swing to increase his average driving distance, is concerned that his driving accuracy will be lower. Which of the two estimates, y-intercept or slope, will help you determine if the golfer’s concern is a valid one? Explain.

Question 3 10.23

Survey of the top business schools. Each year, the Wall Street Journal and Harris Interactive track the opinions and experiences of college recruiters for large corporations and summarize the results in the Business School Survey. In 2005, the survey included rankings of 76 business schools. Survey data for the top 10 business schools are given in the table below. All the data are saved in theBSCHOOL file.

School	Enrollment (# full-time students)	Annual Tuition ($)	Mean GMAT	% with Job Offer	Avg. Salary ($)
Dartmouth	503	38,400	704	—	119,800
Michigan	1,873	33,076	690	91	105,986
Carnegie Mellon	661	38,800	691	93	95,531
Northwestern	2,650	38,844	700	94	117,060
Yale	468	36,800	696	86	104,018
Pennsylvania	1,840	40,458	716	92	117,471
Cal., Berkeley	1,281	21,512	701	92	112,699
Columbia	1,796	38,290	709	95	126,319
North Carolina	855	16,375	652	86	92,565
Southern Cal.	1,588	37,558	685	82	88,839

Source: “Wall Street Journal’s annual rankings of business schools,” The Wall Street Journal, Sep. 21, 2005. Copyright 2005 by Dow Jones & Company, Inc. in the format Textbook via Copyright Clearance Center.

a. Select one of the variables as the dependent variable, y, and another as the independent variable, x. Use your knowledge of the subject area and common sense to help you select the variables.

b. Fit the simple linear model, E(y) = β0 + β1x, to the data in the BSCHOOLfile. Interpret the estimates of the slope and y-intercept

Question 4 11.3

Suppose you fit the multiple regression model

y = β0 + β1x1 + β2x2 + β3x3 + ε

to n = 30 data points and obtain the following result:

ŷ = 3.4 – 4.6x1 + 2.7x2 + .93x3

The estimated standard errors of  and  are 1.86 and .29, respectively.

a. Test the null hypothesis H0: β2 = 0 against the alternative hypothesis Ha:β2 ≠ 0. Use α = .05.

b. Test the null hypothesis H0: β3 = 0 against the alternative hypothesis Ha:β3 ≠ 0. Use α = .05.

c. The null hypothesis H0: β2 = 0 is not rejected. In contrast, the null hypothesis H0: β3 = 0 is rejected. Explain how this can happen even though.

Question 5 11.12

Trust in e-retailers. Electronic commerce (or “e-commerce”) describes the use of electronic networks to simplify a business operation. With e-commerce, retailers now can advertise and sell their products easily over the Web. In Internet Research: Electronic Networking Applications and Policy (Vol. 11, 2001), Canadian researchers investigated the factors that impact the level of trust in Web e-retailers. Five quantitative independent variables were used to model level of trust (y):

x1	= ease of navigation on the Web site
x2	= consistency of the Web site
x3	= ease of learning the Web interface
x4	= perception of the interface design
x5	= level of support available to the user

a. Write a first-order model for level of trust as a function of the five independent variables.

b. The model, part a, was fit to data collected for n = 66 visitors to e-retailers’ Web sites and yielded a coefficient of determination of R2 = .58. Interpret this result.

c. Compute the F-statistic used to test the global utility of the model.

d. Using α = .10, give the appropriate conclusion for the test, part c.