The accompanying data file contains information on 30 employee’s annual pick errors (Errors), experience (Exper in years), and whether or not the employee attended training (Train equals 1 if the employee attended training, 0 otherwise). Model 1 predicts Errors using Exper and Train as predictor variables. Model 2 includes Exper and Train along with an interaction between the two. 

a. Use the holdout method to compare the predictability of the models using the first 20 observations for training and the remaining 10 observations for validation. 

b. Use the k-fold cross-validation method to compare the predictability of the models using k = 3.