Solve the following questions using Minitab only

2 (3+3-6 points) The uniformity of a silicon wafer following an etching process is determined by measuring the layer thickness at several locations and expressing uniformity as the range of the thicknesses Following are uniformity determinations for 30 consecutive wafers processed through the etching tool Wafer Uniformity Wafer Uniformit 15 16 17 18 19 20 21 16 12 16 14 34 4 18 13 18 12 13 12 15 21 21 14 13 23 24 25 26 27 28 29 30 10 23 12 13 15 (a) Is there evidence that uniformity is normally distributed? (b) Construct the required control chart. Is the process in statistical control? Revise the control limits as necessary