Formulas and Tables

Individuals and moving range chart formulas

The most common (and recommended) method of computing control limits for an individuals chart based on 3 standard deviations is:

Individuals (X)

Upper control limit

Lower control limit

Moving Range

Upper control limit

Lower control limit

Tabular values for X and range charts
Subgroup
Size
E2
D4
1
2.660
3.268
2
2.660
3.268
3
1.772
2.574
4
1.457
2.282
5
1.290
2.114
6
1.184
2.004
7
1.109
1.924
8
1.054
1.864
9
1.010
1.816
10
0.975
1.777