Sigma chart calculations

Sigma chart control limits are calculated as follows:

Sigma chart calculations

Control Limits calculated from

Control Limits calculated from
standard deviation (s ) are


is calculated using subgroup standard deviations instead of subgroup ranges. For more information, see Estimated Sigma.


NOTE: If subgroup size is variable, m is replaced with mi for ith subgroup limits. When subgroup size is variable, the control limit values will not be the same; therefore, the chart may display `city skyline' type control lines.

Data Plot Items

Descriptive Statistics

See Also

Quality Chart Formula Reference

Sigma chart

Sigma chart properties

Configuring a Sigma chart

XBar-S chart