# Metrology

Measurement uncertainty, guard bands, conformity decisions, gauge repeatability and reproducibility, and operator variation.

[Manufacturing Wiki](https://planar.so/wiki/index.md)

- [Calibration intervals](https://planar.so/wiki/inspection/metrology/calibration-intervals.md): Setting and reviewing recalibration schedules using measurement needs, drift, usage, checks, and consequences rather than a universal annual rule.
- [Cp process capability](https://planar.so/wiki/inspection/metrology/cp-process-capability.md): Tolerance-to-spread ratio, estimation assumptions, within versus overall variation and limits on interpreting capability.
- [Cpk process capability](https://planar.so/wiki/inspection/metrology/cpk-process-capability.md): Centering-sensitive capability, within versus overall variation, one-sided limits, confidence bounds and interpretation.
- [Gauge repeatability and reproducibility](https://planar.so/wiki/inspection/metrology/gauge-repeatability-and-reproducibility.md): Designing and interpreting Gage R&R studies without confusing precision, bias, variance percentages and tolerance consumption.
- [Guard bands in conformity assessment](https://planar.so/wiki/inspection/metrology/guard-bands-in-conformity-assessment.md): Separating specification and acceptance limits, selecting uncertainty-aware decision rules, and interpreting false-accept and false-reject risks.
- [Instrument resolution](https://planar.so/wiki/inspection/metrology/instrument-resolution.md): Display increments, effective discrimination, quantization uncertainty and practical limits on selecting measurement equipment.
- [Measurement bias](https://planar.so/wiki/inspection/metrology/measurement-bias.md): Estimating systematic measurement offsets against references, with controls for correction, range, uncertainty and decision use.
- [Measurement decision rules](https://planar.so/wiki/inspection/metrology/measurement-decision-rules.md): Choosing, agreeing, applying, and reporting uncertainty-aware conformity decisions without confusing a measured result with acceptance.
- [Measurement repeatability](https://planar.so/wiki/inspection/metrology/measurement-repeatability.md): Precision under defined short-term conditions, repeatability study design, standard-deviation estimation and uncertainty limits.
- [Measurement reproducibility](https://planar.so/wiki/inspection/metrology/measurement-reproducibility.md): Evaluating precision under changed measurement conditions, with clear study boundaries, variance models and uncertainty limits.
- [Measurement traceability](https://planar.so/wiki/inspection/metrology/measurement-traceability.md): Connecting measurement results to stated references through calibration chains, uncertainties, competent services, and controls during use.
- [Measurement uncertainty](https://planar.so/wiki/inspection/metrology/measurement-uncertainty.md): Measurement models, Type A/B evaluation, combined and expanded uncertainty, worked budgets and conformity decisions.
- [Pp process performance](https://planar.so/wiki/inspection/metrology/pp-process-performance.md): Interpreting Pp as specification width relative to overall process spread, with centering, sampling and distribution limits.
- [Ppk process performance](https://planar.so/wiki/inspection/metrology/ppk-process-performance.md): Calculating and interpreting overall process performance with representative data, explicit variation estimators, distribution checks, and uncertainty about the index.
- [Reference standards](https://planar.so/wiki/inspection/metrology/reference-standards.md): Metrological reference and working standards, certified reference materials, traceability, certificate interpretation and continued validity.
- [Sampling length in surface measurement](https://planar.so/wiki/inspection/metrology/sampling-length-in-surface-measurement.md): Separating legacy sampling lengths, ISO 21920 evaluation and section lengths, filter scales and digital point spacing.
- [Surface roughness cutoff length](https://planar.so/wiki/inspection/metrology/surface-roughness-cutoff-length.md): Interpreting profile-filter settings, legacy sampling lengths, ISO 21920 nesting indices, and evaluation lengths without assuming a universal cutoff.

## Related guides

- [Calibration certificates](https://planar.so/wiki/sourcing/documents/calibration-certificates.md): How calibration results, corrections, uncertainty, traceability and conformity statements describe different aspects of measurement evidence.