The table below shows the control chart line constants:
| Averages |
Ranges |
Standard Deviations |
||||
|---|---|---|---|---|---|---|
|
Samples in Group |
A2 |
D2* |
D3 |
D4 |
B3 |
B4 |
|
1 |
2.660 |
1.128 |
0 |
3.267 |
0 |
3.267 |
|
2 |
1.880 |
0 |
3.267 |
0 |
3.267 |
|
|
3 |
1.023 |
0 |
2.574 |
0 |
2.568 |
|
|
4 |
0.729 |
0 |
2.282 |
0 |
2.266 |
|
|
5 |
0.577 |
0 |
2.114 |
0 |
2.089 |
|
|
6 |
0.483 |
0 |
2.004 |
0.030 |
1.970 |
|
|
7 |
0.419 |
0.076 |
1.924 |
0.118 |
1.882 |
|
|
8 |
0.373 |
0.136 |
1.864 |
0.185 |
1.815 |
|
|
9 |
0.337 |
0.184 |
1.816 |
0.239 |
1.761 |
|
|
10 |
0.308 |
0.223 |
1.777 |
0.284 |
1.716 |
|
|
10 |
0.308 |
0.223 |
1.777 |
0.284 |
1.716 |
|
|
11 |
0.285 |
0.256 |
1.744 |
0.321 |
1.679 |
|
|
12 |
0.266 |
0.283 |
1.717 |
0.354 |
1.646 |
|
|
13 |
0.249 |
0.307 |
1.693 |
0.382 |
1.618 |
|
|
14 |
0.235 |
0.328 |
1.672 |
0.406 |
1.594 |
|
|
15 |
0.223 |
0.347 |
1.653 |
0.428 |
1.572 |
|
|
16 |
0.212 |
0.363 |
1.637 |
0.448 |
1.552 |
|
|
17 |
0.203 |
0.378 |
1.622 |
0.466 |
1.534 |
|
|
18 |
0.194 |
0.391 |
1.608 |
0.482 |
1.518 |
|
|
19 |
0.187 |
0.403 |
1.597 |
0.497 |
1.503 |
|
|
20 |
0.180 |
0.415 |
1.585 |
0.510 |
1.490 |
|
|
21 |
0.173 |
0.425 |
1.575 |
0.523 |
1.477 |
|
|
22 |
0.167 |
0.434 |
1.566 |
0.534 |
1.466 |
|
|
23 |
0.162 |
0.443 |
1.557 |
0.545 |
1.455 |
|
|
24 |
0.157 |
0.451 |
1.548 |
0.555 |
1.445 |
|
|
25 |
0.153 |
0.459 |
1.541 |
0.565 |
1.435 |
|
* D2 is only used for estimating standard deviation when there is one sample per subgroup.
Reference ANSI Z1.1-1985, Z1.2-1985 & Z1.3-1985: American National Standard, Guide for Quality Control Charts, Control Chart Method of Analyzing Data, Control Chart Method of Controlling Quality During Production.
Hints
Double-click the chart area on an SPC page to display the SPC Genie and change the SPC variables.
The tools and menu items in these procedures automatically open the Citect SCADA form for you. Move the cursor till it changes to a hand to find these tools or options.
Published June 2018