A psychiatrist wants to know whether the level of pathology (Y) in psychotic patients 6 months after treatment can be predicted with reasonable accuracy from knowledge of pretreatment symptom ratings of thinking disturbance (X1) and hostile suspiciousness (X2). The following table lists data collected on 53 patients.

a. The least-squares equation involving both independent variables is given by Ŷ = -0.0635 + 23.451X1 - 7.073X2. Using this equation, determine the predicted level of pathology for a patient with pretreatment scores of 2.80 on thinking disturbance and 7.0 on hostile suspiciousness. How does this predicted value compare with the value actually obtained for patient 5?
b. Sums of squares are shown next for three regression models. Determine the R2-values for each of these models. If you use R2 and model simplicity as selection criteria, which model appears to be the best?