A manufacturing company produces cylindrical tubes for engines that are specified to be 1.20 centimeters thick. As part of the company€™s statistical quality-control effort, random samples of four tubes are taken each hour. The tubes are measured to determine whether they are within thickness tolerances. Shown here are the thickness data in centimeters for nine samples of tubes. Use these data to develop an xÌ„ chart and an R chart. Comment on whether or not the process appears to be in control at thispoint.

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Sample 1 1.22 1.19 1.20 1.23 Sample 2 1.20 1.20 1.22 1.20 Sample 3 1.21 1.18 1.17 1.20 Sample 4 1.16 1.17 1.20 1.16 Sample 5 1.24 1.20 1.21 1.18 Sample 6 1.19 1.21 1.21 1.20 Sample 7 1.24 1.17 1.18 1.19 Sample 8 1.17 1.23 1.22 1.16 Sample 9 1.22 1.17 1.16 1.19