10.1. The tensile strength of a paper product is related to the amount of hardwood In the pulp. Ten samples are produced In the pllot plant, and the data obtained are shown In the following table. Parcent Parcent Strength Hardwood Strength Hardwood 160 10 181 20 171 15 108 25 175 15 193 25 182 20 195 28 184 20 200 30 Fit a linear regression model relating strength to percent hardwood. [b) Test the model In part (8) for significance of regression. 10.2. Plot the residuals from Problem 10.1 and comment on model adequacy.10.55. 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. Roac Brake Octane Horsepower rpm Number Compression 225 2000 05 100 212 1800 94 95 229 2400 110 222 1900 91 96 219 1600 100 278 2500 96 110 246 3000 94 98 237 3200 05 100 2800 105 224 3400 BE 97 223 1800 05 100 230 2500 104 Fit a multiple linear regression model to the 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? 10.21. The value of the adjusted A" statistic always Increases when a new regressor variable is added to the model. True False