Specification & Process Data
units
units
units
units
Capability Gauge (Cpk)
Cpk value--
00.671.001.331.67
Awaiting Input
Capability Indices
Cp (Potential)
--
Cpk (Actual)
--
Ppk (Same as Cpk)*
--
Centering Index (K)
--
Defect Rate (PPM)
--ppm
Sigma Level (Z)
--σ
Guidelines & Formulas
Cp = (USL‑LSL)/(6σ)
Cpk = min[(USL‑μ)/(3σ), (μ‑LSL)/(3σ)]
Cpk ≥ 1.33 → capable, 1.00→1.33 → marginal, <1.00 → incapable
Sigma level Z = min(ZU, ZL)
PPM = (Φ(-ZL) + Φ(-ZU)) × 1,000,000
Normal Distribution & Spec Limits
Process Centering & Spread vs Specs