CPK¶
Category: EGTools-only function
Process capability index Cpk from measurements and spec limits.
Syntax¶
=CPK(data, [usl], [lsl])
Arguments¶
| Argument | Required | Description |
|---|---|---|
| data | Required | measurement range or array |
| usl | Optional | upper spec limit (optional if LSL given) |
| lsl | Optional | lower spec limit (optional if USL given) |
Returns¶
Returns the process capability index Cpk = min((USL-μ)/3σ, (μ-LSL)/3σ) as a scalar number. Missing data or both limits missing returns #VALUE!; fewer than 2 numeric values returns #NUM!; a zero standard deviation returns #DIV/0!.
Examples¶
| Formula | Result | Description |
|---|---|---|
=CPK({1;2;3;4;5},5,0) |
0.421637021 | Cpk for spec limits 0 to 5 |
Notes¶
- Uses the sample standard deviation (n-1).
- If only one limit is given, only that side is evaluated.
- USL·LSL accept arrays and are computed element-wise, spilling an array of the same shape — scalars are broadcast, a column vector × a row vector expands to their outer product, size-mismatched elements yield #N/A, and an error element returns that error.
- Related function: CP
- Supported: Excel 2010+. Always registered as
CPKon every Excel version.