In: Statistics and Probability
15.28 Note: This exercise requires a computer and
statistical software. The data mentioned below can be found in
several formats on your Premium Website under "Chapter
datasets".
Information describing 98 of the top automobile dealership groups
in the United States is provided in computer database file DEALERS.
For calendar year 1999, the data include the number of dealers, the
average number of retail units sold per dealer, and the total
revenue for the dealership group. Determine the regression equation
estimating total revenue as the dependent variable and the average
retail units sold per dealer as the independent variable. (SOURCE:
Automotive News, May 1, 2000, pp. 54-60.)
a. The estimated intercept is .
b. The estimated slope is .
c. When the average number of retail units sold per dealer is 1000, the predicted total revenue is .
d. When the average number of retail units sold per dealer is 1000, the lower bound of the 95% confidence interval of total revenue is .
e. When the average number of retail units sold per dealer is 1000, the upper bound of the 95% confidence interval of total revenue is .
f. When the average number of retail units sold per dealer is 1000, the lower bound of the 95% prediction interval of total revenue is .
g. When the average number of retail units sold per dealer is 1000, the upper bound of the 95% prediction interval of total revenue is
Name | RetailUnits | UsedUnits | FleetUnits | TotalUnits | NumDealrs | AvgRetail/Dealer | $GroupRevenue |
AutoNation Inc. | 468981 | 238168 | 186470 | 893619 | 290 | 1617.2 | 20926200000 |
Asbury Automotive Group | 102000 | 66000 | 7000 | 175000 | 84 | 1214.3 | 4231000000 |
V.T., Inc. | 80445 | 58151 | 4886 | 143482 | 35 | 2298.4 | 3317960000 |
Sonic Automotive, Inc. | 74065 | 47345 | 5229 | 126639 | 114 | 649.7 | 3100030000 |
Hendrick Automotive Group | 61861 | 38097 | 3096 | 103054 | 60 | 1031.0 | 2522280000 |
Group 1 Automotive Inc. | 60384 | 45630 | 6136 | 112150 | 47 | 1284.8 | 2364300000 |
Bill Heard Enterprises Inc. | 34714 | 27037 | 610 | 62631 | 11 | 3155.8 | 1433200000 |
Planet Automotive | 31511 | 19779 | 10085 | 61375 | 18 | 1750.6 | 1305980000 |
Lithia Motors Inc. | 28645 | 23840 | 2791 | 55276 | 45 | 636.6 | 1242660000 |
Larry H. Miller Group | 27166 | 31027 | 4589 | 62782 | 34 | 799.0 | 1360930000 |
Penske Automotive Group | 26403 | 5718 | 6506 | 38627 | 5 | 5280.6 | 987415000 |
Serra Investments Inc. | 22291 | 13272 | 2194 | 37757 | 19 | 1173.2 | 824130000 |
Rosenthal Automotive | 22106 | 8220 | 191 | 30517 | 15 | 1473.7 | 791469000 |
DarCars Ltd. | 20605 | 10665 | 1697 | 32967 | 18 | 1144.7 | 732210000 |
Ed Morse Automotive | 20326 | 10991 | 6882 | 38199 | 18 | 1129.2 | 907398000 |
Herb Chambers Cos. | 19871 | 8139 | 0 | 28010 | 15 | 1324.7 | 800772000 |
Holman Enterprises | 19851 | 11495 | 54424 | 85770 | 18 | 1102.8 | 2145490000 |
Faulkner Organization | 19239 | 12588 | 5979 | 37806 | 20 | 962.0 | 806317000 |
Wilson Automotive | 18792 | 6850 | 1275 | 26917 | 7 | 2684.6 | 671818000 |
Tuttle-Click Automotive | 18534 | 7972 | 902 | 27408 | 9 | 2059.3 | 684652000 |
Earnhardt Dealer Grp | 17672 | 11030 | 0 | 28702 | 6 | 2945.3 | 680386000 |
Bob Rohrman Auto Group | 17251 | 18195 | 2 | 35448 | 25 | 690.0 | 639300000 |
Galpin Motors, Inc. | 16686 | 3867 | 8561 | 29114 | 4 | 4171.5 | 616372000 |
Toresco Enterprises | 14928 | 5688 | 841 | 21457 | 6 | 2488.0 | 495067000 |
Braman Dealerships | 14814 | 6060 | 0 | 20874 | 8 | 1851.8 | 685413000 |
Phil Long Dealerships | 14765 | 15234 | 1799 | 31798 | 12 | 1230.4 | 638715000 |
Ourisman Automotive | 14756 | 5513 | 2052 | 22321 | 10 | 1475.6 | 549126000 |
Ricart Automotive | 14653 | 11621 | 638 | 26912 | 3 | 4884.3 | 491776000 |
Don Massey Cadillac | 14217 | 12233 | 423 | 26873 | 22 | 646.2 | 920000000 |
West-Herr Automotive | 13793 | 4945 | 1572 | 20310 | 10 | 1379.3 | 387482000 |
Lou Fusz Automotive | 13704 | 7572 | 252 | 21528 | 11 | 1245.8 | 477370000 |
McCombs Automotive | 13683 | 8661 | 2668 | 25012 | 8 | 1710.4 | 542509000 |
Gillman Cos. | 13463 | 4332 | 0 | 17795 | 13 | 1035.6 | 397293000 |
Allen Samuels Enter. | 13459 | 5169 | 3591 | 22219 | 9 | 1495.4 | 523149000 |
Hitchcock Automotive | 13455 | 4592 | 0 | 18047 | 6 | 2242.5 | 429086000 |
Burt Automotive Network | 13108 | 10005 | 21001 | 44114 | 6 | 2184.7 | 998760000 |
Ferman Automotive | 13059 | 6630 | 335 | 20024 | 13 | 1004.5 | 472695000 |
Suburban Collection | 12680 | 4681 | 586 | 17947 | 14 | 905.7 | 426689000 |
Holler Automotive Group | 12347 | 6175 | 1242 | 19764 | 9 | 1371.9 | 397117000 |
Huffines Auto Group | 11468 | 4079 | 281 | 15828 | 5 | 2293.6 | 431187000 |
Germain Motor Co. | 11331 | 5826 | 120 | 17277 | 6 | 1888.5 | 439549000 |
Fletcher Jones Auto. Grp. | 11305 | 5853 | 805 | 17963 | 7 | 1615.0 | 676774000 |
Wolfe Automotive Group | 11302 | 7896 | 874 | 20072 | 15 | 753.5 | 422513000 |
Keyes Automotive Group | 11259 | 6374 | 163 | 17796 | 7 | 1608.4 | 496801000 |
Sheehy Auto Stores | 11198 | 4549 | 329 | 16076 | 7 | 1599.7 | 367675000 |
World Class Automotive | 11128 | 5276 | 2274 | 18678 | 4 | 2782.0 | 427939000 |
Jeff Wyler Dealer Group | 11009 | 6089 | 1374 | 18472 | 6 | 1834.8 | 361841000 |
Kelley Automotive Group | 10976 | 7308 | 211 | 18495 | 12 | 914.7 | 446452000 |
Kenwood Dealer Grp. | 10878 | 5993 | 0 | 16871 | 10 | 1087.8 | 350158000 |
Hudiburg Auto Group | 10823 | 13633 | 678 | 25134 | 8 | 1352.9 | 501479000 |
Bob Baker Auto Group | 10771 | 6386 | 886 | 18043 | 7 | 1538.7 | 434858000 |
Chapman Automotive | 10740 | 6203 | 1639 | 18582 | 9 | 1193.3 | 519192000 |
Pohanka Automotive | 10375 | 5404 | 0 | 15779 | 13 | 798.1 | 438126000 |
Wilde Automotive Group | 10176 | 7717 | 16 | 17909 | 11 | 925.1 | 369823000 |
Miller Automotive Grp. | 10162 | 6015 | 0 | 16177 | 3 | 3387.3 | 375632000 |
Hays Automotive Group | 10035 | 10672 | 1378 | 22085 | 9 | 1115.0 | 433603000 |
Bergstrom Automotive | 9953 | 8044 | 911 | 18908 | 19 | 523.8 | 435755000 |
Prestige Mgmt. Services | 9805 | 1698 | 0 | 11503 | 7 | 1400.7 | 457865000 |
Swope Group | 9767 | 11224 | 764 | 21755 | 22 | 444.0 | 442308000 |
Day Automotive Group | 9470 | 5192 | 1239 | 15901 | 13 | 728.5 | 312666000 |
Ray Catena Motor Car | 9197 | 3098 | 0 | 12295 | 5 | 1839.4 | 521279000 |
Cutter Mgmt. Co. | 9196 | 6565 | 125 | 15886 | 13 | 707.4 | 372202000 |
Piercey Automotive Grp. | 9159 | 3282 | 0 | 12441 | 4 | 2289.8 | 291500000 |
Lupient Automotive Grp. | 9050 | 7900 | 8000 | 24950 | 12 | 754.2 | 494500000 |
Midway Auto Team | 9007 | 4078 | 12744 | 25829 | 2 | 4503.5 | 558491000 |
Kahlig Enterprises | 8932 | 5523 | 673 | 15128 | 4 | 2233.0 | 374281000 |
Boucher Group Inc. | 8901 | 8946 | 761 | 18608 | 14 | 635.8 | 381249000 |
Warnock Automotive Grp. | 8519 | 1769 | 5114 | 15402 | 6 | 1419.8 | 408300000 |
Scott-McRae Automotive | 8393 | 9003 | 3763 | 21159 | 5 | 1678.6 | 391736000 |
Joe Myers Dealership | 8382 | 4126 | 1058 | 13566 | 4 | 2095.5 | 293656000 |
Carl Gregory Enterprises | 8372 | 8648 | 250 | 17270 | 14 | 598.0 | 308095000 |
Chapman Auto Group | 8265 | 5820 | 487 | 14572 | 8 | 1033.1 | 331137000 |
Ancira Enterprises | 8161 | 4764 | 8438 | 21363 | 9 | 906.8 | 502865000 |
Motorcars Group | 8154 | 4267 | 0 | 12421 | 12 | 679.5 | 314134000 |
DeCastro Automotive Grp. | 8113 | 4411 | 512 | 13036 | 6 | 1352.2 | 262453000 |
Performance Cos. | 8084 | 7416 | 455 | 15955 | 10 | 808.4 | 390063000 |
Hall Auto World Inc. | 7962 | 5140 | 836 | 13938 | 12 | 663.5 | 305319000 |
Rosatti Auto Group | 7836 | 1736 | 0 | 9572 | 2 | 3918.0 | 203386000 |
Rick Case Enterprises Inc. | 7833 | 4159 | 0 | 11992 | 9 | 870.3 | 227533000 |
Russ Darrow Group | 7800 | 5800 | 11300 | 24900 | 11 | 709.1 | 497000000 |
Mel Farr Automotive Grp. | 7782 | 6028 | 3893 | 17703 | 8 | 972.8 | 421665000 |
Ira Motor Group | 7735 | 2842 | 0 | 10577 | 3 | 2578.3 | 293217000 |
Noarus Auto Group | 7673 | 3733 | 0 | 11406 | 5 | 1534.6 | 268584000 |
Servco Pacific Inc. | 7657 | 3674 | 1628 | 12959 | 9 | 850.8 | 264788000 |
Don Bohn/Bohn Bros. | 7648 | 3073 | 55 | 10776 | 4 | 1912.0 | 222347000 |
Stewart Mgmt. Group Inc. | 7632 | 4314 | 200 | 12146 | 4 | 1908.0 | 257051000 |
AutoFair Automotive Group | 7478 | 3781 | 55 | 11314 | 5 | 1495.6 | 307117000 |
Lamarque Automotive Grp. | 7440 | 5132 | 1145 | 13717 | 5 | 1488.0 | 315644000 |
Vista Auto | 7276 | 2715 | 0 | 9991 | 5 | 1455.2 | 270542000 |
Gunn Automotive Group | 7272 | 5201 | 31 | 12504 | 8 | 909.0 | 263951000 |
Classic Automotive Group | 7087 | 4082 | 88 | 11257 | 4 | 1771.8 | 258771000 |
Ron Tonkin Family | 7021 | 11372 | 833 | 19226 | 17 | 413.0 | 391730000 |
Marubani Motor Services | 7015 | 2915 | 0 | 9930 | 14 | 501.1 | 305000000 |
Cuillo Group | 6832 | 4210 | 0 | 11042 | 6 | 1138.7 | 319961000 |
Mathews Auto Group | 6577 | 7160 | 0 | 13737 | 8 | 822.1 | 223077000 |
Gettel Automotive Group | 6545 | 3654 | 60 | 10259 | 6 | 1090.8 | 214133000 |
Farmer Automotive Group | 6451 | 5630 | 264 | 12345 | 4 | 1612.8 | 275564000 |
Kenny Ross Automotive | 6428 | 6601 | 322 | 13351 | 5 | 1285.6 | 236410000 |
Considering only the required columns ie AvgRetail/Dealer and $GroupRevenue
When we run regression in excel we get the following result
SUMMARY OUTPUT | ||||||
Regression Statistics | ||||||
Multiple R | 0.006981818 | |||||
R Square | 4.87458E-05 | |||||
Adjusted R Square | -0.010367413 | |||||
Standard Error | 2164593622 | |||||
Observations | 98 | |||||
ANOVA | ||||||
df | SS | MS | F | Significance F | ||
Regression | 1 | 2.19271E+16 | 2.19271E+16 | 0.00468 | 0.945602158 | |
Residual | 96 | 4.49805E+20 | 4.68547E+18 | |||
Total | 97 | 4.49827E+20 | ||||
Coefficients | Standard Error | t Stat | P-value | Lower 95% | Upper 95% | |
Intercept | 828663848.7 | 419024769.6 | 1.977601108 | 0.050841 | -3093745.049 | 1660421442 |
X Variable 1 | 15875.08814 | 232060.6096 | 0.068409232 | 0.945602 | -444761.5812 | 476511.7575 |
a. The estimated intercept is
828663848.7 |
b. The estimated slope is
15875.08814 |
c. When the average number of retail units sold per dealer is 1000, the predicted total revenue is
= intercept + x * slope = 828663848.7 + 1000 * 15875.08814 = 844538936.8
d. When the average number of retail units sold per dealer is 1000, the lower bound of the 95% confidence interval of total revenue is
-447855326 |
ie a loss of 447855326
e. When the average number of retail units sold per dealer is 1000, the upper bound of the 95% confidence interval of total revenue is .intercept + 1000 * slope at 95% upper bound
2136933200 |