---
alias: user-guide-number-of-defects
description: "This documentation details a chart analyzing defect counts using statistical properties"
---

# Number Of Defects (c)

The following table lists the properties of the Number of Defects (c) chart.

| Property                                            | Description                                                       |
|-----------------------------------------------------|--------------------------------------------------------------------|
| **Chart**                                          | Number of Defects *(c)*                                     |
| **Process observation types**                      | Attributes                                              |
| **Process observations relationships**             | Independent                                             |
| **Sample Size**                                    | Constant                                                |
| **Distribution type**                              | Poisson                                                 |
| **Size of shift to detect**                        | Large (≥ 1.5σ)                                          |
| **Number of Defects (Indicator 1)**                | $c=number\;of\;defects$      |
| **Number of Defects (Indicator 2)**                | ***Not applicable***                                                                     |
| **Standard Deviation**   | $s = \sqrt{\overline{c}}$<br/>Where $\overline{c}$ is the centerline |
| **Number of Defects (Indicator 1) Centerline**     | $\overline{c}=\frac{c_1+c_2+\cdots+c_k}{k}$<br/>where *c* is the number of defects per sample             |
| **Number of Defects (Indicator 1) Control Limits** | $UCL=\overline{c}+3s$<br/>$LCL = max(\overline{c}-3s;0)$|
| **Indicator 2 Centerline**                         | ***Not applicable***                                        |
| **Indicator 2 Control Limits**                     | ***Not applicable***                                        |

Table: Number of Defects chart properties