Fraction Defective (p)#
The following table lists the properties of the Fraction Defective (p) chart.
| Property | Description |
|---|---|
| Chart | Fraction Defective (p) |
| Process observation types | Attributes |
| Process observations relationships | Independent |
| Sample Size | Variable, usually >=50 |
| Distribution type | Binomial |
| Size of shift to detect | Large (≥ 1.5σ) |
| Fraction Defective (Indicator 1) | \(p=\frac{number\;of\;rejects}{number\;inspected}\) |
| Fraction Defective (Indicator 2) | Not applicable |
| Standard Deviation for sample | \(s = \sqrt{\frac{\overline{p}(1-\overline{p})}{n}}\) Where \(\overline{p}\) is the centerline and \(n\) is the sample size which can vary by sample |
| Fraction Defective (Indicator 1) Centerline | \(\overline{p}=\frac{total\;number\;of\;rejects}{total\;number\;inspected}\) |
| Fraction Defective (Indicator 1) Control Limits | \(UCL = min(\overline{p}+3s;1)\) \(LCL = max(\overline{p}-3s;0)\) |
| Indicator 2 Centerline | Not applicable |
| Indicator 2 Control Limits | Not applicable |
Table: Fraction Defective chart properties