In-Control

An “In-Control” process is one that is free of assignable/special causes of variation. Stable, in-control, with random variation only, all mean the same thing which is, the process behaves equally over the time. Such a condition is most often evidence on a control chart which displays an absence of nonrandom variation.

In control refers to a process unaffected by special causes. A process that is in control is affected only by common causes. A process that is out of control is affected by special causes in addition to the common causes affecting the mean and/or variance.

Also see Stable Process.