Out-of-control signals (rule violations) occur in a variety of situations, but all the signals indicate a change in the process where it is considered to be abnormal, or out of control. Some signals include: six points in a row that are increasing or decreasing, eight points in a row that are farther than one standard deviation away from the centerline, or fourteen points in a row that are alternating up and down. When used properly, these signals can identify important changes that can help to improve or maintain the process.
SPC in MES
SPC Control Charts