Select the method or formula of your choice.
The zone chart classifies observations or subgroup means according to their distance from the center line. For each observation or subgroup mean, the corresponding plot point is derived as follows.
You can specify weights other than 0, 2, 4, and 8 for the zone scores. You can also choose to reset the cumulative score after each signal.
Zone score or weight of .
Sum of sequential weights. Each time a new point crosses the center line, the sum is reset to zero.
The center line represents the process average, μ. For a zone chart, μ is the overall average of the individual observations or subgroup averages when the subgroup size is constant.
The default zone chart uses for μ, the pooled standard deviation for σ when subgroup size > 1, and the average moving range for σ when subgroup size = 1.