Publications and Resources on Statistical Process Control (SPC):
Publications -
- Part 1: Introduction to SPC
- Part 2: How and Why SPC Works
- Part 3: Pareto Analysis and Check Sheets
- Part 4: Flowcharts
- Part 5: Cause-and-Effect Diagrams
- Part 6: Design of Experiments
- Part 7: Variables Control Charts
- Part 8: Attributes Control Charts
- Part 9: Process Capability Analysis
Excel spreadsheet for creating ͞X and R charts for SPC.
| Factors for estimating σ from ͞R and ͞s (σ = ͞R ÷ d2; σ = ͞s ÷ c4) | |||
| Number of observations in subgroup (n) | d2 | c4 | |
| 2 | 1.128 | 0.7979 | |
| 3 | 1.693 | 0.8862 | |
| 4 | 2.059 | 0.9213 | |
| 5 | 2.326 | 0.9400 | |
| 6 | 2.534 | 0.9515 | |
| 7 | 2.704 | 0.9594 | |
| 8 | 2.847 | 0.9650 | |
| 9 | 2.970 | 0.9693 | |
| 10 | 3.078 | 0.9727 | |
| 11 | 3.173 | 0.9754 | |
| 12 | 3.258 | 0.9776 | |
| 13 | 3.336 | 0.9794 | |
| 14 | 3.407 | 0.9810 | |
| 15 | 3.472 | 0.9823 | |
| 16 | 3.532 | 0.9835 | |
| 17 | 3.588 | 0.9845 | |
| 18 | 3.640 | 0.9854 | |
| 19 | 3.689 | 0.9862 | |
| 20 | 3.735 | 0.9869 | |
| 21 | 3.778 | 0.9876 | |
| 22 | 3.819 | 0.9882 | |
| 23 | 3.858 | 0.9887 | |
| 24 | 3.895 | 0.9892 | |
| 25 | 3.931 | 0.9896 | |
| 30 | 4.086 | 0.9914 | |
| 35 | 4.213 | 0.9927 | |
| 40 | 4.322 | 0.9936 | |
| 45 | 4.415 | 0.9943 | |
| 50 | 4.498 | 0.9949 | |
| 55 | 4.572 | 0.9954 | |
| 60 | 4.639 | 0.9958 | |
| 65 | 4.699 | 0.9961 | |
| 70 | 4.755 | 0.9964 | |
| 75 | 4.806 | 0.9966 | |
| 80 | 4.854 | 0.9968 | |
| 85 | 4.898 | 0.9970 | |
| 90 | 4.939 | 0.9972 | |
| 95 | 4.978 | 0.9973 | |
| 100 | 5.015 | 0.9975 | |
| Factors for determining from ͞R the 3σ control limits for ͞X and R charts | |||
| Factors for R Chart | |||
| Number of observations in subgroup (n) | Factor for ͞X chart, A2 | Lower Control | Upper Control |
| 2 | 1.880 | 0 | 3.267 |
| 3 | 1.023 | 0 | 2.574 |
| 4 | 0.729 | 0 | 2.282 |
| 5 | 0.577 | 0 | 2.114 |
| 6 | 0.483 | 0 | 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 |
| 11 | 0.285 | 0.256 | 1.744 |
| 12 | 0.266 | 0.283 | 1.717 |
| 13 | 0.249 | 0.307 | 1.693 |
| 14 | 0.235 | 0.328 | 1.672 |
| 15 | 0.223 | 0.347 | 1.653 |
| 16 | 0.212 | 0.363 | 1.637 |
| 17 | 0.203 | 0.378 | 1.622 |
| 18 | 0.194 | 0.391 | 1.608 |
| 19 | 0.187 | 0.403 | 1.597 |
| 20 | 0.180 | 0.415 | 1.585 |
| 21 | 0.173 | 0.425 | 1.575 |
| 22 | 0.167 | 0.434 | 1.566 |
| 23 | 0.162 | 0.443 | 1.557 |
| 24 | 0.157 | 0.451 | 1.548 |
| 25 | 0.153 | 0.459 | 1.541 |
| Factors for determining from ͞s the 3σ control limits for ͞X and s charts | |||
| Factors for s Chart | |||
| Number of observations in subgroup (n) | Factor for ͞X chart, A3 | Lower Control | Upper Control |
| 2 | 2.659 | 0 | 3.267 |
| 3 | 1.954 | 0 | 2.568 |
| 4 | 1.628 | 0 | 2.266 |
| 5 | 1.427 | 0 | 2.089 |
| 6 | 1.287 | 0.030 | 1.970 |
| 7 | 1.182 | 0.118 | 1.882 |
| 8 | 1.099 | 0.185 | 1.815 |
| 9 | 1.032 | 0.239 | 1.761 |
| 10 | 0.975 | 0.284 | 1.716 |
| 11 | 0.927 | 0.321 | 1.679 |
| 12 | 0.886 | 0.354 | 1.646 |
| 13 | 0.850 | 0.382 | 1.618 |
| 14 | 0.817 | 0.406 | 1.594 |
| 15 | 0.789 | 0.428 | 1.572 |
| 16 | 0.763 | 0.448 | 1.552 |
| 17 | 0.739 | 0.466 | 1.534 |
| 18 | 0.718 | 0.482 | 1.518 |
| 19 | 0.698 | 0.497 | 1.503 |
| 20 | 0.680 | 0.510 | 1.490 |
| 21 | 0.663 | 0.523 | 1.477 |
| 22 | 0.647 | 0.534 | 1.466 |
| 23 | 0.633 | 0.545 | 1.455 |
| 24 | 0.619 | 0.555 | 1.445 |
| 25 | 0.606 | 0.565 | 1.435 |
