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+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