Special Cause Variation Testing

A method of applying a set of tests to a process to see if special causes exist. The method includes eight common tests typically applied to a control that splits the area into 3 zones (called A, B, & C) representing one standard deviation away from the mean. The tests evaluate the variation of the process and look for the following occurrences in the data: 1) any data point outside the control limits, 2) nine data points in a row on the same side of the mean, 3) six data points in a row either all increasing or decreasing, 4) fourteen data points in a row alternating up and down, 5) two of three consecutive data points on the same side of the mean in zone A or beyond, 6) four of five consecutive data points on the same side of the mean in Zone B or beyond, 7) fifteen consecutive data points within Zone C on either side of the mean, and 8) eight consecutive data points outside of Zone C on either side of the mean.
Related StatStuff Video: 
   -Section 5-Measure Phase, Lesson #16 - Testing for Special Cause Variation