2.6 In fitting a model to classify prospects as purchasers or nonpurchasers, a certain com- pany drew the training data from internal data that include demographic and purchase information. Future data to be classified will be lists purchased from other sources, with demographic (but not purchase) data included. It was found that refund issued was a useful predictor in the training data. Why is this not an appropriate variable to include in the model? 2.8 Normalize the data in Table 2.7, showing calculations. TABLE 2.7 Age Income ($) 25 56 65 32 41 49 49,000 156,000 99,000 192,000 39,000 57,000 2.6 In fitting a model to classify prospects as purchasers or nonpurchasers, a certain com- pany drew the training data from internal data that include demographic and purchase information. Future data to be classified will be lists purchased from other sources, with demographic (but not purchase) data included. It was found that refund issued was a useful predictor in the training data. Why is this not an appropriate variable to include in the model? 2.8 Normalize the data in Table 2.7, showing calculations. TABLE 2.7 Age Income ($) 25 56 65 32 41 49 49,000 156,000 99,000 192,000 39,000 57,000