More Info Factors for calculating three-sigma limits for the x-chart and R-char At Quick Car Wash, the wash process is advertised to take less than 6 minutes. Consequently, management has set a target average of 340 seconds for the wash process. Suppose the average range for a sample of 9 cars is 8 seconds. Use the accompanying table to establish control limits for sample means and ranges for the car wash process. Click the icon to view the table of factors for calculating three-sigma limits for the x-chart and R-chart. The UCLR equals seconds and the LCLR equals seconds. (Enter your responses rounded to two decimal places.) The UCLx equals seconds and the LCLx equals seconds. (Enter your responses rounded to two decimal places.)