Dirt bikes 2014, revisited. The model in Exercise 30 is missing one predictor that we might have expected to see.

Engine Displacement is highly correlated 1r = 0.7832 with MSRP, but that variable has not entered the model (and, indeed, would have a P-value of 0.54 if it were added to the model). Here is some evidence to explain why that may be.

(Hint: Notice that Displacement is the response variable in this regression.)

Response variable is: Displacement R squared = 95.7% R squared (adjusted) = 95.5%

s = 29.88 with 59 - 4 = 55 degrees of freedom Variable Coefficient SE(Coeff) t-ratio P-value Intercept -228.722 34.65 -6.60 60.0001 Rake 0.500980 0.2286 2.19 0.0326 Wheel Base -1.74909 0.9312 -1.88 0.0656 Bore 7.77225 0.3180 24.4 60.0001

a) What term describes the reason Displacement doesn’t contribute to the regression model for MSRP?

b) Find the value of the Variance Inf lation Factor for Displacement in the regression on MSRP.