Home

Western Electric Company (WECO) Rules

This page is designed to give a probability plot of the time to signaling an alarm (the run-length), for a Shewhart control chart with or without supplementary run rules.

Tell me more about control charts and WECO rules.

Enter your process parameters:
Size of process shift The size of shift that you want to detect, in standardized units. Between 0 and 5
Rule to apply No rule
2 of the last 3 points fall in [-3,-2] or [2,3]
4 of the last 5 points fall in [-3,-1] or [1,3]
8 consecutive points fall on one side of the center line

Create your own rule: consecutive points fall in zone   ± [ , ]
     		Each rule states an event that causes the plot to signal an alarm. Create your own rule:  ± [2.5, 3] means between [-3, -2.5] or [2.5, 3]
Maximal run length value The largest value that should be on the probability plot

Random quote

Quality is free, but only to those who are willing to pay heavily for it.

— Philip Crosby