Control Chart

Time-series chart of a process metric with statistical limits — separates common from special causes.

Also known as: control chart, SPC chart, Shewhart chart

A control chart (SPC chart, Shewhart chart) plots a process metric over time (individual values, subgroup means, proportions, counts) with a centre line and two control limits (UCL/LCL). It is the standard tool of the Control phase.

Variables charts — for continuous measurements: I-MR, X̄-R, X̄-S
Attribute charts — for count data: p/np chart, c/u chart
Time-weighted charts — for small persistent shifts: EWMA, CUSUM
Special forms — short-run, multivariate (Hotelling T²), rare-event (g/t)

Used in

Control Chart
Control Chart (Attribute)
Control Chart (Time-Weighted)
Control Chart (Short-Run Z-MR)
Multivariate Control Chart (Hotelling T²)
Control Chart (Rare Events)
Control Chart (Box-Cox transformed)
Run Chart

In the Algorithm Lab

control-charts/control-chart
control-charts/attribute-control-chart
control-charts/time-weighted-chart

Sources

Shewhart, W. A. — Economic Control of Quality of Manufactured Product, Van Nostrand, 1931
Montgomery, D. C. — Introduction to Statistical Quality Control, 8th Edition, Wiley
AIAG — Statistical Process Control (SPC) Reference Manual, 2nd Edition, 2005