Run of seven is shop shorthand for the most widely used run rule: seven points in a row above or below the centerline, or seven in a row each higher or lower than the last. The chance of seven points landing on one named side by luck alone is 1 in 128, so a run that long usually marks a small sustained shift or a drift. Some rule sets use eight or nine points instead of seven to cut false alarms.
No single point is out, but that's a run of seven below center since the new pad went on. Something moved.
Also heard as
- seven in a row
- run
- trend
Related terms
Western Electric rules
Standard set of run rules that flag nonrandom patterns on a control chart, not just single points past the limits.
Shift
Sudden, sustained step change in a process mean, often after a maintenance event, material change or recipe edit.
Drift
Slow, steady creep of a process or gauge reading in one direction as something wears, depletes or ages.
OOC
Out of control: shorthand for a point or chart that has violated a control limit or run rule.