A study was performed on wear of a bearing y and its relationship to x1 = oil viscosity and x2 = load. The following data were obtained. (a) Fit a multiple linear regression model to these data. (b)...

A study was performed on wear of a bearing y and its relationship to x1 = oil viscosity and x2 = load. The following data were obtained.

(a) Fit a multiple linear regression model to these data.


(b) Estimate s2 and the standard errors of the regression coefficients.

(c) Use the model to predict wear when x1 = 25 and x2 = 1000.

(d) Fit a multiple linear regression model with an interaction term to these data.

(e) Estimate s2 and se(Bj) for this new model. How did these quantities change?

Does this tell you anything about the value of adding the interaction term to the model?

(f) Use the model in (d) to predict when x1 = 25 and x2 = 1000. Compare this prediction with the predicted value from part (b) above.