The accompanying file contains 400 observations with the binary response variable y along with the predictor variables x₁, x₂, x₃, and x₄.

a. Perform KNN analysis on the data set. What is the optimal value of k?

b. Report the accuracy, specificity, sensitivity, and precision rates and the AUC value for the test data set (for Analytic Solver) or validation data set (for R).

c. What is the lift value of the leftmost bar shown in the decile-wise lift chart?

d. Score the new observations in the Exercise_9.7_Score worksheet. What are the predicted response values of the first two new observations?