The U. S. Department of Energy's Fuel Economy Guide provides fuel efficiency data for cars and trucks (U. S. Department of Energy website, February 22, 2008). A portion of the data for 311 compact, midsize, and large cars follows. The column labeled Class identifies the size of the car; Compact, Midsize, or Large. The column labeled Displacement shows the engine's displacement in liters. The column labeled Fuel Type shows whether the car uses premium (P) or regular (R) fuel, and the column labeled HwyMPG shows the fuel efficiency rating for highway driving in terms of miles per gallon. a. Develop an estimated regression equation that can be used to predict the fuel efficiency for highway driving, given the engine's displacement.
Let x represent the engine's displacement.
If required, round your answers to four decimal places. For subtractive or negative numbers use a minus sign even if there is a + sign before the blank. (Example: -300)
Y = ___ + ___ x

b. How much of the variation in the sample values of HwyMPG does this estimated regression equation explain?