Np chart properties |
Configuring an Np
chart | Np chart
calculations

The Np chart is an attribute control chart that measures the
number of nonconforming items in a sample of constant size. The Np
chart is identical to the P chart, except that the actual number of
nonconforming items is plotted, rather than the proportion of the
sample. Also, the Np chart's sample size must be constant, while
the P chart's samples can be constant or varied.

In the following Np chart example, the y-axis shows the number
of nonconforming items for each sample. In this case, the sample
size is set as a constant (1000). 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