Problem 10-3 The time to replace vehicle wiper blades at a service center was monitored using a mean and a range chart. Six samples of n = 20 observations have been obtained and the sample means and ranges computed: Range Range .46 Sample 1 2 3 Mean 3.06 3.15 3.11 .42 .50 Sample 4 5 6 Mean 3. 13 3.06 3.09 .46 41 .45 Factors for three-sigma control limits for i and R charts Factors for three-sigma control limits for and R charts Factor for X Chart, A2 Number of Observations in Subgroup, n 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1.88 1.02 0.73 0.58 0.48 0.42 0.37 0.34 0.31 0.29 0.27 0.25 0.24 0.22 0.21 0.20 0.19 0.19 0.18 FACTORS FOR R CHARTS Lower Upper Control Control Limit, Limit, D3 D4 0 3.27 2.57 0 2.28 2.11 0 2.00 0.08 1.92 0.14 1.86 0.18 1.82 0.22 1.78 0.26 1.74 0.28 1.72 0.31 1.69 0.33 1.67 0.35 1.65 0.36 1.64 0.38 1.62 0.39 1.61 0.40 1.60 0.41 1.59 a. Using the factors in the above table, determine upper and lower limits for mean and range charts. (Do not round intermediate calculations. Round your mean value to 3 decimal places and range value to 4 decimal places.) Upper limit for mean Lower limit for mean Upper limit for range Lower limit for range b. Is the process in control? Yes