Appendix A: SPC Constants Tables
Appendix A SPC Constants Tables A.1 Purpose of SPC Constants SPC constants are statistically derived factors used to calculate control limits for different control charts. These constants depend on sample size (n) and are essential for constructing X̄–R, X̄–S, R, and S charts accurately. A.2 Control Chart Constants for X̄–R Charts Table A.1: Constants A₂, D₃, and D₄ Sample Size (n) A₂ D₃ D₄ 2 1.880 0.000 3.267 3 1.023 0.000 2.574 4 0.729 0.000 2.282 5 0.577 0.000 2.114 6 0.483 0.000 2.004 7 0.419 0.076 1.924 8 0.373 0.136 1.864 9 0.337 0.184 1.816 10 0.308 0.223 1.777 15 0.223 0.347 1.653 20 0.180 0.414 1.585 25 0.153 0.459 1.541 Usage X̄-chart limits : [ UCL = \bar{X} + A_2 \bar{R} ] [ LCL = \bar{X} - A_2 \bar{R} ] R-chart limits : [ UCL = D_4 \bar{R} ] [ LCL = D_3 \bar{R} ] A.3 Control Chart Constants for X̄–S Charts Table A.2: Constants A₃, B₃, and B₄ Sample Size (n) A₃ B₃ B₄ 2 2.659 0.000 3.267 3 1.954 0.000 2.568 4 1.628 0.000 2.266 5 1.427 0.000 2.089 6 1.287 0.030...