Factors for three-sigma control limits for X and R charts Number of Observations in Subgroup, 6 0.08 8 Factor for X Chart, A2 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 3.27 232 2.57 2.28 2.11 2.00 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 1.59 16 17 18 19 20 0.41 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