Passenger Car Mileage

Story Name: Passenger Car Mileage

Abstract: Variation in gasoline mileage among makes and models of automobiles is influenced substantially by the weight and horsepower of the vehicles. When miles per gallon and horsepower are transformed to logarithms, the linearity of the regression is improved. A negative second order term is required to fit the logarathmic mileage to weight relation. If the logged variables are standardized, the coefficients of the first order terms indicate the standard units change in log mileage per one standard unit change in the predictor variable at the (logarithmic) mean. This change is constant in the case of mileage to horsepower, but not for mileage to weight. The coefficient of the second order weight term indicates the change in standardized slope associ- ated with a one standard deviation increase in the logarithm of weight. Reference: R.M. Heavenrich, J.D. Murrell, and K.H. Hellman, Light Duty Automotive Technology and Fuel Economy Trends Through 1991, U.S. Environmental Protection Agency, 1991 (EPA/AA/CTAB/91-02). Authorization: free use Description: Based on data provided by the U.S. Environmental Protection Agency Number of cases: 82 Variable Names:

1.VOL: Cubic feet of cab space 2.HP: Engine horspower 3.MPG: Average miles per gallon 4.SP: Top speed (mph) 5.WT: Vehicle weight (100 lb)

The Data:

MAKE MODEL VOL HP MPG SP WT GM/GeoMetroXF1 89 49 65.4 96 17.5 GM/GeoMetro 92 55 56.0 97 20.0 GM/GeoMetroLSI 92 55 55.9 97 20.0 SuzukiSwift 92 70 49.0 105 20.0 DaihatsuCharade 92 53 46.5 96 20.0 GM/GeoSprintTurbo 89 70 46.2 105 20.0 GM/GeoSprint 92 55 45.4 97 20.0 HondaCivicCRXHF 50 62 59.2 98 22.5 HondaCivicCRXHF 50 62 53.3 98 22.5 DaihatsuCharade 94 80 43.4 107 22.5 SubaruJusty 89 73 41.1 103 22.5 HondaCivicCRX 50 92 40.9 113 22.5 HondaCivic 99 92 40.9 113 22.5 SubaruJusty 89 73 40.4 103 22.5 SubaruJusty 89 66 39.6 100 22.5 SubaruJusty4wd 89 73 39.3 103 22.5 ToyotaTercel 91 78 38.9 106 22.5 HondaCivicCRX 50 92 38.8 113 22.5 ToyotaTercel 91 78 38.2 106 22.5 FordEscort 103 90 42.2 109 25.0 HondaCivic 99 92 40.9 110 25.0 PontiacLeMans 107 74 40.7 101 25.0 IsuzuStylus 101 95 40.0 111 25.0 DodgeColt 96 81 39.3 105 25.0 GM/GeoStorm 89 95 38.8 111 25.0 HondaCivicCRX 50 92 38.4 110 25.0 HondaCivicWagon 117 92 38.4 110 25.0 HondaCivic 99 92 38.4 110 25.0 Subaru Loyale 102 90 29.5 109 25.0 VolksJettaDiesel 104 52 46.9 90 27.5 Mazda323Protege 107 103 36.3 112 27.5 FordEscortWagon 114 84 36.1 103 27.5 FordEscort 101 84 36.1 103 27.5 GM/GeoPrism 97 102 35.4 111 27.5 ToyotaCorolla 113 102 35.3 111 27.5 EagleSummit 101 81 35.1 102 27.5 NissanCentraCoupe 98 90 35.1 106 27.5 NissanCentraWagon 88 90 35.0 106 27.5 ToyotaCelica 86 102 33.2 109 30.0 ToyotaCelica 86 102 32.9 109 30.0 ToyotaCorolla 92 130 32.3 120 30.0 ChevroletCorsica 113 95 32.2 106 30.0 ChevroletBeretta 106 95 32.2 106 30.0 ToyotaCorolla 92 102 32.2 109 30.0 PontiacSunbirdConv 88 95 32.2 106 30.0 DodgeShadow 102 93 31.5 105 30.0 DodgeDaytona 99 100 31.5 108 30.0 EagleSpirit 111 100 31.4 108 30.0 FordTempo 103 98 31.4 107 30.0 ToyotaCelica 86 130 31.2 120 30.0 ToyotaCamry 101 115 33.7 109 35.0 ToyotaCamry 101 115 32.6 109 35.0 ToyotaCamry 101 115 31.3 109 35.0 ToyotaCamryWagon 124 115 31.3 109 35.0 OldsCutlassSup 113 180 30.4 133 35.0 OldsCutlassSup 113 160 28.9 125 35.0 Saab9000 124 130 28.0 115 35.0 FordMustang 92 96 28.0 102 35.0 ToyotaCamry 101 115 28.0 109 35.0 ChryslerLebaronConv 94 100 28.0 104 35.0 DodgeDynasty 115 100 28.0 105 35.0 Volvo740 111 145 27.7 120 35.0 FordThunderbird 116 120 25.6 107 40.0 ChevroletCaprice 131 140 25.3 114 40.0 LincolnContinental 123 140 23.9 114 40.0 ChryslerNewYorker 121 150 23.6 117 40.0 BuickReatta 50 165 23.6 122 40.0 OldsTrof/Toronado 114 165 23.6 122 40.0 Oldsmobile98 127 165 23.6 122 40.0 PontiacBonneville 123 165 23.6 122 40.0 LexusLS400 112 245 23.5 148 40.0 Nissan300ZX 50 280 23.4 160 40.0 Volvo760Wagon 135 162 23.4 121 40.0 Audi200QuatroWag 132 162 23.1 121 40.0 BuickElectraWagon 160 140 22.9 110 45.0 CadillacBrougham 129 140 22.9 110 45.0 CadillacBrougham 129 175 19.5 121 45.0 Mercedes500SL 50 322 18.1 165 45.0 Mercedes560SEL 115 238 17.2 140 45.0 JaguarXJSConvert 50 263 17.0 147 45.0 BMW750IL 119 295 16.7 157 45.0 Rolls-RoyceVarious 107 236 13.2 130 55.0