In This Topic
Cp
Notation
| Term | Description |
|---|---|
| USL | Upper specification limit |
| LSL | Lower specification limit |
| Toler | Multiplier of the sigma tolerance (Minitab uses 6 as the default value) |
 | Within-subgroup standard deviation |
Cpk
PPM Total for expected "within" performance
The expected number of parts per million that are outside the specification limits, based on the variation within the subgroups, is
Notation
| Term | Description |
|---|---|
| PPM | Parts per million |
| LSL | Lower specification limit |
| USL | Upper specification limit |
| Φ (X) | Cumulative distribution function (CDF) of a standard normal distribution |
 | Average of the observations |
| s | Within-subgroup standard deviation |
Z.LSL, Z.USL, and Z.Bench for potential (within) capability
Benchmark Z statistics for potential capability are calculated by finding the Z value using the standard normal (0,1) distribution for the corresponding statistics.
where:
Notation
| Term | Description |
|---|---|
| Φ (X) | Cumulative distribution function (CDF) of a standard normal distribution |
| Φ-1 (X) | Inverse CDF of a standard normal distribution |
 | Within-subgroup standard deviation |
