Compute Cg = (USL − LSL)/(6·s) from specification limits and measurement process standard deviation; Cg ≥ 1.33 is generally required.
输入上/下规格限与测量标准差 s，求 Cg。
| Item | Formula / Note | Source / Standard |
|---|---|---|
| Measurement capability index | Cg = tolerance / (K · sigma_m), commonly with K = 6 | ISO 22514-7:2012, Statistical methods in process management - Capability of measurement processes |
| Twenty percent rule | Measurement variation should generally not exceed 20% of the tolerance | AIAG, Measurement Systems Analysis (MSA) Reference Manual, 4th ed. (2010) |
| Acceptance criterion | Cg ≥ 1.33 is commonly required to accept the measurement process | ISO 22514-7:2012, Statistical methods in process management - Capability of measurement processes |
| Relation to capability indices | Formally parallels the process capability index Cp, applied to the measurement process | ISO 22514-7:2012, Statistical methods in process management - Capability of measurement processes |