10. Alico Steel manufacturers steel tubes that are used in gas grills for residential customers. The tube's overall length is crucial to assure a proper fit, and this dimension has been targeted as an important dimension to be stabilized for the steel tube manufacturing process. Gas grill performance and customer safety are key objectives and highlight the importance of producing high quality steel tubes. Tubes are cut from rolls of steel tubing using a punch press. The tubes are measured using an operationally defined method and the table below summarizes the results. Tube Length (in centimeters) Sample Observations 1 to 6 Number Average x-bar Average range 12.90 0.35 13.30 0.50 12.87 0.32 10.93 0.44 11.43 0.91 11.93 0.42 12.90 0.29 13.03 0.58 13.70 0.21 10 13.70 0.11 Total 126.69 4.13 a. The centerline for the trial x-bar chart is The centerline for the trial R-chart is