a. Set up an x-chart with n=4. The frequency should be sample four and then skip four. Thus, your first sample would be for minutes 1 - 4, the second would be for minutes 9-12, and so on. Compute the mean, x, for each sample. (Enter your responses rounded to two decimal places.) Sample 1 2 3 4 5 6 7 8 9 Minutes 1-4 9-12 17-20 25-28 33-36 41 - 44 49-52 57-60 65-68 X 20.75 20.00 18.75 19.75 20.50 21.25 19.75 21.00 19 10 73-76 22.25 The UCL; equals minutes and the LCL, equals minutes. (Enter your responses rounded to two decimal places.) The Precision Machining Company makes hand-held tools on an assembly line that produces one product every minute. On one of the products, the critical quality dimension is the diameter (measured in thousandths of an inch) of a hole bored in one of the assemblies. Management wants to detect any shift in the process average diameter from 0.020 in. Management considers the variance in the process to be in control. Historically, the average range has been 0.0025 in., regardless of the process average. Design an x-chart to control this process, with a center line at 0.020 in, and the control limits set at three sigmas from the center line. Management provided the results of 80 minutes of output from the production line, as shown in the table below. During these 80 minutes, the process average changed once. All measurements are in thousandths of an inch. 18 21 22 22 Minutes 1 -12 13-24 25-36 37 - 48 49-60 61 - 72 73 - 80 20 20 19 23 17 20 21 21 21 18 21 22 21 23 SNARSS Sample data for Precision Machining Company Diameter (thousandths of an inch) 23 19 21 22 20 19 19 21 19 19 18 19 20 20 22 23 20 21 20 19 21 21 19 22 23 24 21 19 20 22 19 21 20 22 23 18 19 19 21 22 23 21 22 19 22 88882 ARS 21 20 21 21 23 22 |S A B 8 ) 20 22 23