Applicable to run charts and control charts, a shift in its most basic form is seven points in a row either above or below the centerline. A trend is seven points in a row in an upward direction or seven points in a row in a downward direction. With a trend, it doesn’t matter if the centerline is crossed.
Use: The use of a shift or a trend is that when seen, it is a ‘smoking gun’ for an area of improvement. The team is really hoping to see a trend or a shift because if a process always stays in the state of statistical control, the opportunity of reducing assignable-cause variation is far more challenging then if assignable-cause variation is evident.
