Analyze the residuals from the regression model in Problem 10.7. Comment on model adequacy.
Problem 10.7:
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:
(a) Fit a multiple regression model to these data.
(b) Test for significance of regression. What conclusions can you draw?
(c) Based on t-tests, do you need all three regressor variables in the model?