If only one predictor (x) variable is used to predict weight, which single variable is best? Why? Predicting Weights of Males. In Exercises 9–12, refer to the accompanying table, which was obtained by using the data for males in Data Set 1 “Body Data” in Appendix B. The response (y) variable is weight (kg), and the predictor (x) variables are HT (height in cm), WAIST (waist circumference in cm), and ARM (arm circumference in cm).