A capability index is a numerical ratio that measures how well a process's natural variation fits within specified tolerance limits, calculated as the ratio of allowed spread to actual spread (e.g., Cp = (USL - LSL) / 6σ, Cpk adjusts for centering). It quantifies process conformance to specifications and determines whether a process is capable of consistently producing output within required bounds. The metric persists through statistical reporting, quality management systems, and control charts where it guides process improvement decisions. [formal: index-capabilitatis | substrate: behavior | horizon: a moment | explicit: yes | epoch: 0.09]
Accepted ontology entry
capability index
A capability index is a numerical ratio that measures how well a process's natural variation fits within specified tolerance limits, calculated as the ratio of allowed spread to actual spread (e.g., Cp = (USL - LSL) / 6σ, Cpk adjusts for c…
Definition
Why it is in scope
A statistical measure (such as Cp, Cpk, Pp, Ppk) that quantifies how well a process meets specification limits. Human-made as a quantitative metric for assessing process performance relative to tolerances.
Names and aliases
- capability indexen · CANONICAL
Relations from this entry
- cmsjrtp9z03j7nobpei5zyp4eINSTANCE_OF →
A capability index (Cp, Cpk, Pp, Ppk) IS a specific quantitative measure of process capability. Nearest kind: capability indices are process-capability metrics, not general metrics (process-capability is nearer). Which-came-first: process-capability as concept predates formal Cp/Cpk indices.
- cmrw30hzx003tekzzxacxtt4sSERVES →
A capability index is built to further the operation of quality control — its designed purpose is to inform quality decisions by quantifying how well a process meets specifications. For whose sake? The index serves quality control. Law 8d.
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Record identity
- Created
- Aug 8, 2026, 3:43 AM UTC
- Content hash
- bf322383abebae1ba88ff3274d2aa692d825b25969ff689cce08b2aa2089f9cf