U chart properties |
Configuring a U chart |
U chart calculations

The U chart is an attribute control chart that shows the number
of nonconformities (defects or discrepancies) that are found in a
samples subgroup. U charts are the same as C charts, except that
the U chart measures the average number of nonconformities from
samples of variable or constant sizes, whereas C chart subgroups
are the same size.

In the following U chart example, the y-axis shows the number of
nonconformities in each sample subgroup. The subgroups are of
variable size. The control limits (shown on the chart as UCL, CL,
LCL, WL1, and WL2) are set according to the data and a sigma limit
of 3.

### See Also