5. SPC Control: Line Display

The SPC Control Properties dialog box>Lines tab enables you to select  whether to display/hide each of the control lines and zones.

Check  each line type or zone that should display on the chart.

1	UCL	Upper Control Limit
2	CL	Center Line
3	LCL	Lower Control Limit
4	Zones	A, B, C

Notes

Zones are as follows.

Zone	Area
C	Up to one standard deviation from the center line.
B	Between one and two standard deviations from the center line.
A	Between two and three standard deviations from the center line.

In general, a control chart consists of the center line corresponding to the average value at which the quality characteristic should perform, and lines corresponding to the upper and lower control limits for the characteristic. The upper and lower control limits are also referred to as the upper and lower three-sigma control limits.