The brake horsepower developed by an automobile engine on a dynamometer is thought to be a function of the engine speed in revolutions per minute (rpm), the road octane number of the fuel, and the engine compression.An experiment is run in the laboratory and the data that follow are collected. The data is used for regression analysis and the following results are gained:

Minitab Output Regression Analysis: Horsepower versus rpm, Octane, Compression Predictor Coef SE Coef P VIF Constant -266.03 92 . 67 -2.87 0 . 021 rpm 0 . 010713 0 . 004483 2.39 0 . 044 1.0 Octane 3. 1348 0 . 8444 3. 71 0 . 006 1. 0 Compress 1. 8674 0. 5345 3. 49 0 . 008 1.0 S = 8. 812 R-Sq = 80.78 R-Sq (adj ) = 73.4% PRESS = 2494.05 R-Sq (pred) = 22.338