Quality Advisor

A free online reference for statistical process control, process capability analysis, measurement systems analysis, control chart interpretation, and other quality metrics.

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:

Individuals moving range upper control limits formula

Lower control limit:

individuals & moving range lower control limit formula

Moving Range

moving range formula

average moving range formula

Upper control limit:

moving range upper control limit

Lower control limit:

moving range 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

Point, click, chart.

Real-time data analytics
and statistical process control!

Learn More   Request a Free Trial