The term statistical control is somewhat of a misnomer. It does not mean that statistics controls the process but that there is statistical evidence that it is in control. Statistical control results from quality control of a measurement process. Moreover, the individual values will be distributed about the limiting mean in a stable distribution described by a stable standard deviation. The data output of a system in statistical control has statistical predictability, and various statistical calculations may be made to describe and evaluate it. Statistical control is necessary to evaluate the precision of a process but says nothing about bias. However, it is a prerequisite for the evaluation of bias. It is useless to try to identify bias until statistical control has been attained and the variability of the process has been evaluated.