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Process Capability Cp and Cpk, Step by Step
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Mean
Specs, Mean, and Sigma
Mean
Specs, Mean, and Sigma
Spec Limits
Mean
Sigma
The mean places the process inside the spec band.
highlighted = computed this step
Mean
The process mean is 52.
mean
=
52
\text{mean} = 52
mean
=
52
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
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