Problem 11.2 Refer to Example 10.3 of Chapter 10.

(a) State the matrix formulation of the the Model (Y = shear strength |X = weld diameter).

(b) Write down the normal equations for this model in the matrix format 11.4.

(c) Verify that βˆ0 = −216.325, βˆ1 = 3.9904 satisfy the normal equations.

(d) Compute the estimated variance–covariance matrix s2(X X)−1.