WECO Rules 
The following table lists the Western Electric Company (WECO) rule numbers, which can be displayed on SPC charts with alarms. The {LIMIT} and {LENGTH} tags are replaced when the query for the chart is executed.
Rule Number | Description |
1 | Outside of control limits |
2 | {LIMIT} of {LENGTH} points above or below centerline |
3 | {LIMIT} of {LENGTH} points steadily increasing or decreasing |
4 | {LIMIT} of {LENGTH} points alternating trend direction |
5 | {LIMIT} of {LENGTH} in Zone A or beyond |
6 | {LIMIT} of {LENGTH} in Zone B or beyond |
7 | {LIMIT} of {LENGTH} points between +/- 1 sigma |
8 | {LIMIT} points not between +/- 1 sigma |
See also: