Mean | y | y | Mean of the forecast values |
Standard deviation | y | y | Standard deviation of the forecast values |
Cp | n | y | Short-term capability index indicating what quality level the forecast output is potentially capable of producing. It is defined as the ratio of the specification width to the forecast width. If a Cp is equal to or greater than 1, then a short-term 3-sigma quality level is possible. |
Pp | y | n | Long-term capability index indicating what quality level the forecast output is potentially capable of producing. It is defined as the ratio of the specification width to the forecast width. If a Cp is equal to or greater than 1, then a long-term 3-sigma quality level is possible. |
Cpk-lower | n | y | One-sided short-term capability index; for normally distributed forecasts, the ratio of the difference between the forecast mean and lower specification limit over three times the forecast short-term standard deviation; often used to calculate process capability indices with only a lower specification limit. |
Ppk-lower | y | n | One-sided long-term capability index; for normally distributed forecasts, the ratio of the difference between the forecast mean and lower specification limit over three times the forecast long-term standard deviation; often used to calculate process capability indices with only a lower specification limit. |
Cpk-upper | n | y | One-sided short-term capability index; for normally distributed forecasts, the ratio of the difference between the forecast mean and upper specification limit over three times the forecast short-term standard deviation; often used to calculate process capability indices with only an upper specification limit. |
Ppk-upper | y | n | One-sided long-term capability index; for normally distributed forecasts, the ratio of the difference between the forecast mean and upper specification limit over three times the forecast long-term standard deviation; often used to calculate process capability indices with only an upper specification limit. |
Cpk | n | y | Short-term capability index (minimum of calculated Cpk-lower and Cpk-upper) that takes into account the centering of the forecast with respect to the midpoint of the specified limits; a Cpk equal to or greater than 1 indicates a quality level of 3 sigmas or better. |
Ppk | y | n | Long-term capability index (minimum of calculated Ppk-lower and Ppk-upper) that takes into account the centering of the forecast with respect to the midpoint of the specified limits; a Ppk equal to or greater than 1 indicates a quality level of 3 sigmas or better. |
Cpm | n | y | Short-term Taguchi capability index; similar to Cpk but considers a target value, which may not necessarily be centered between the upper and lower specification limits. |
Ppm | y | n | Long-term Taguchi capability index; similar to Ppk but considers a target value, which may not necessarily be centered between the upper and lower specification limits. |
Z-LSL | y | y | The number of standard deviations between the forecast mean and the lower specification limit. |
Z-USL | y | y | The number of standard deviations between the forecast mean and the upper specification limit. |
Zst | y | n | For short-term metrics when only one specification limit is defined, equal to Z-LSL if there is only a lower specification limit or Z-USL if there is only an upper specification limit. |
Zst-total | n | y | For short-term metrics when both specification limits are defined, the number of standard deviations between the short-term forecast mean and the lower boundary of combining all defects onto the upper tail of the normal curve. Also equal to Zlt-total plus the Z-score shift value if a long-term index is available. |
Zlt | n | y | For long-term metrics when only one specification limit is defined, equal to Z-LSL if there is only a lower specification limit or Z-USL if there is only an upper specification limit. |
Zlt-total | y | n | For long-term metrics when both specification limits are defined, the number of standard deviations between the long-term forecast mean and the lower boundary of combining all defects onto the upper tail of the normal curve. Also equal to Zst-total minus the Z-score shift value if a short-term index is available. |
p(N/C)-below | y | y | Probability of a defect below the lower specification limit; DPUBELOW |
p(N/C)-above | y | y | Probability of a defect above the upper specification limit; DPUABOVE |
p(N/C)-total | y | y | Probability of a defect outside the lower and upper specification limits; DPUTOTAL |
PPM-below | y | y | Defects below the lower specification limit, per million units |
PPM-above | y | y | Defects above the upper specification limit, per million units |
PPM-total | y | y | Defects outside both specification limits, per million units |
LSL | y | y | Lower specification limit, the lowest acceptable value of a forecast involved in process capability, or quality, analysis. |
USL | y | y | Upper specification limit, the highest acceptable value of a forecast involved in process capability analysis. |
Target | y | y | The ideal target value of a forecast involved in process capability analysis. |
Z-score shift | y | y | An optional shift value to use when calculating long-term capability metrics. The default, set in the Capability Options panel, is 1.5. |