=+42. Soluble dietary fiber (SDF) can provide health benefits by lowering blood cholesterol and glucose levels. The article “Effects of Twin-Screw Extrusion on Soluble Dietary Fiber and Physicochemical Properties of Soybean Residue” (Food Chemistry, 2013:

884–889) reported the following data on y 5 SDF content (%) in soybean residue and the three predictors x1 5 extrusion temperature (in C), x2 = feed moisture (in %), and x3 5 screw speed (in rpm) of a twin-screw extrusion process.

Obs x1 x2 x3 y 1 35 110 160 11.13 2 25 130 180 10.98 3 30 110 180 12.56 4 30 130 200 11.46 5 30 110 180 12.38 6 30 110 180 12.43 7 30 110 180 12.55 8 25 110 160 10.59 9 30 130 160 11.15 10 30 90 200 10.55 11 30 90 160 9.25 12 25 90 180 9.58 13 35 110 200 11.59 14 35 90 180 10.68 15 35 130 180 11.73 16 25 110 200 10.81 17 30 110 180 12.68