The plotted points represent the defect rate for each subgroup, :
Data points on a U chart follow the Poisson distribution.
Term | Description |
---|---|
![]() | number of defects for subgroup ![]() |
![]() | size of subgroup ![]() |
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
.
Term | Description |
---|---|
![]() | number of defects in subgroup ![]() |
![]() | size of subgroup ![]() |
The LCL for each subgroup is the greater of the following:
Term | Description |
---|---|
![]() | process mean |
![]() | parameter for Test 1. The default is 3. |
![]() | size of subgroup ![]() |