Methods and formulas for C Chart

Select the method or formula of your choice.

Plotted points

The plotted points represent the number of defects in each subgroup, .

Center line

The center line represents the process mean, . If you do not specify a historical value, then Minitab uses the mean from your data, , to estimate .


number of defects in subgroup
number of subgroups

Control limits

Lower control limit (LCL)

The LCL is the greater of the following:

Upper control limit (UCL)


process mean
parameter for Test 1. The default is 3. (For more information go to Select tests for special causes for C Chart.)