=+38. An investigation of a die-casting process resulted in the accompanying data on x1 5 furnace temperature, x2 5 die close time, and y 5 temperature difference on the die surface (“A Multiple-Objective DecisionMaking Approach for Assessing Simultaneous Improvement in Die Life and Casting Quality in a Die Casting Process,” Quality Engr., 1994: 371–383).

x1: 1250 1300 1350 1250 1300 x2: 6 7 6 7 6 y: 80 95 101 85 92 x1: 1250 1300 1350 1350 x2: 8 8 7 8 y: 87 96 106 108