The stated goal of a chain of service stores is to provide a lube and oil change for anyone's automobile in 15 minutes. The manager at one store thinks that there is a growing disparity among his workers in the time it takes to lube and change the oil of an automobile. To monitor this, the manager has selected a sample of 20 days and has recorded the time it took five randomly selected employees to service an automobile. The data are found below. Complete parts a through d Click the icon to view the data. a. The manager noticed that the longest time it took to service a car was 25.73 minutes. Suppose the distribution of fimes to service a car was normal, with a mean of 15. Without analyzing the sample data, use your knowledge of a normal distribution to give the manager an estimate for the population standard deviation for the time it takes to service a car. The standard deviation is minutes. (Round to two decimal places as needed.) b. Use the data to construct an x- and an R-chart. Construct a control chart for the range. Which graph below shows an R-chart for the data? Ⓒ A. Construct a control chart for the mean. Which graph below shows an x-chart for the data? OA. OB. OB www Ос ос Mast c. Based on these data, what would you conclude about the service process? OA. Since two points on the x-chart are below the lower control limit, the process is out of control. OB. Since two points on the R-chart are above the upper control limt, the process is out of control. OC. Since ten points in a row are above the centerline on the x-chart, the process is out of control. OD. Since all of the points on the R-chart and x-chart are between the control limits, the process is under control. d. Based on your findings on the R-chart, would it be advisable to draw conclusions based on the x-chart? Data Employee Day 1 2 4 15.13 18.30 13.54 2 12.72 18.36 12.89 15.44 12.50 3 14.00 13.29 11.20 16.83 24.37 4 17.55 13.31 14.44 15.92 5 11.47 25.73 13.10 16.14 21.06 A. Since the R-chart indicates that the process is out of control, the x-chart will indicate that the process is out of control as well. 6 13.78 16.59 19.72 7.21 17.22 OB. Since the R-chart indicates that the process is under control, use the x-chart to draw conclusions 12.54 16.48 1668 17.85 8 14.44 16.28 15.00 16.72 16.13 OC. Since the x-chart uses R to determine the control limits and the R-chart indicates that the process is out of control, do not use the x-chart to draw conclusions OD. Since the x-chart and the R-chart are not related, use the x-chart to draw conclusions 9 1563 15.19 13.08 15.38 15.02 10 15.05 14.35 15.45 1860 14.07 13.04 13.88 16.58 12 20.16 14.13 14.39 15.56 13.32 13 13.76 15.48 19.17 20.31 16.62 14 16.65 12.65 15.18 12.59 16.15 15 14.90 12.47 16.29 13.96 16.54 16 13.84 12.04 15.70 18.37 11.35 17 17.26 16.45 11.35 13.21 15.06 18 16.36 13.16 14.82 16.96 12.45 19 12.21 15.08 16.14 15.15 12.40 20 12.79 17.16 15.12 16.65 13.52 OD. OD.