A control chart indicates when your process is out of control and helps you identify the presence of special-cause variation. When special-cause variation is present, your process is not stable and corrective action is necessary.
Points that fall randomly within the control limits indicate that your process is in control and exhibits only common-cause variation. Points that fall outside the control limits or display a nonrandom pattern, indicate that your process is out of control and that special-cause variation is present.
Whether you are monitoring an ongoing process or trying to obtain more understanding of your new process, control charts can be helpful tools.