A control valve needs to be very sensitive to the input voltage, thus generating a good output voltage. An engineer turns the control bolts to change the input voltage. The book SN-Ratio for the Quality Evaluation, published by the Japanese Standards Association (1988), described a study on how these three factors (relative position of control bolts, control range of bolts, and input voltage) affect the sensitivity of a control valve. The factors and their levels are shown below. The data show the sensitivity of a control valve.

Factor A, relative position of control bolts:

center −0.5, center, and center +0.5 Factor B, control range of bolts:

2, 4.5, and 7 (mm)

Factor C, input voltage:

100, 120, and 150 (V)