1. (a) 

To test the quality of a regression fit use mean squared error.

       1   ₙ
MSE = ───  ∑ (yᵢ - f̂(xᵢ))² 
       n   ⁱ⁼¹



Ave(y₀ - f(x₀))²


To test the quality of a model in the classification settings, use the error rate:

         1   ₙ
    E = ─── ∑ I(yᵢ ≠ ŷᵢ)
         n   ⁱ⁼¹
