Home
/
Process Capability Cp and Cpk, Step by Step
/
Sigma
Specs, Mean, and Sigma
Sigma
Specs, Mean, and Sigma
Spec Limits
Mean
Sigma
Sigma sets the six-sigma comparison width.
highlighted = computed this step
Sigma
The sigma input is 2.
σ
=
2
\sigma = 2
σ
=
2
Capability snapshot
The chart recomputes Cp, Cpu, Cpl, Cpk, and the centered what-if.
process capability Cp and Cpk
Cp 5/3; Cpk 4/3; sigma 2
measure
value
meaning
spec width
20
USL minus LSL
six-sigma width
12
six times sigma
Cp
5/3
width comparison
Cpu
4/3
upper side
Cpl
2
lower side
Cpk
4/3
smaller side
base
LSL 40
USL 60
mean 52
Cpu 4/3; Cpl 2
what-if
LSL 40
USL 60
mean 50
Cpu 5/3; Cpl 5/3
Cp 5/3
base Cpk 4/3
what-if Cpk 5/3
what-if Cpk 5/3; gain 1/3
deterministic process-capability arithmetic only
Previous: Mean
Book TOC