=+Surface Roughness in Ultrasonic Vibration Turning” (J. of Engr. Manuf., 2009: 641–652). The response variable is surface roughness (mm), and the independent variables are vibration amplitude

(mm), depth of cut (mm), feed rate (mm/rev), and cutting speed (m/min), respectively.

The regression equation is Ra = -0.972 - 0.0312a - 0.557d - 18.3f- 0.00282v Predictor Coef SE Coef T P Constant -0.9723 0.3923 -2.48 0.015 a -0.03117 0.01864 -1.67 0.099 d 0.5568 0.3185 1.75 0.084 f 18.2602 0.7536 24.23 0.000 v 0.002822 0.003977 0.71 0.480 S = 0.822059 R–Sq = 88.6% R-Sq(adj) = 88.0%

Source DF SS MS F P Regression 4 401.02 100.25 148.35 0.000 Residual Error 76 51.36 0.68 Total 80 452.38