01 · Purpose
Why and when to use it
Use it as an initial instrument-and-method check before a broader multi-operator assessment.
Who takes part?
The measurement owner works with people who understand the process and the recorded data. Statistical or measurement-system decisions should involve someone able to check the assumptions and study design.
02 · Application
How to apply it
Start with an agreed measurement purpose, explicit units and trustworthy observations. Identify missing cases and assumptions before calculating.
- Choose a traceable reference value and an appropriate tolerance or acceptance basis.
- Control conditions and repeat independent measurements using the real procedure.
- Compute the mean, repeatability standard deviation and bias relative to the reference.
- If using Cg/Cgk, document the tolerance fraction and study-variation multiplier.
- Compare results with decision needs and investigate bias or poor repeatability.
03 · Example
A worked measurement example
Original fictional teaching example. Small datasets illustrate the method; they are not proposed as sufficient study sizes. Supplied parameters are assumptions, not estimates from a real process.
| Input or result | Illustrative value |
|---|---|
| Reference / tolerance width | 100.00 g / 2.00 g |
| Mean / repeatability s | 100.05 g / 0.03 g |
| Bias | 100.05 − 100.00 = +0.05 g |
| Cg, using 20% tolerance and 6s | 0.20 × 2 / (6 × 0.03) = 2.22 |
| Cgk, same convention | (0.10 × 2 − 0.05) / (3 × 0.03) = 1.67 |
04 · Interpretation
What the result tells you
Bias reduces Cgk relative to Cg. The calculation uses stated conventions and supplied study estimates; it does not establish performance with other operators or at other reference levels.
Completion check: A one-reference repeatability and bias assessment under documented conditions.
05 · Judgement
Mistakes and limitations
Do not confuse gage capability with process Cp/Cpk. No universal threshold is imposed here; use the applicable measurement requirements and account for reference uncertainty.
07 · Reading
Sources and further reading
The tool list follows the accepted LeanTrainingLab overview and its reference to Six Sigma+Lean Toolset, second edition (Lunau, editor; Springer, 2013). The book chapters were not available for direct review during this build. Explanations, examples and worksheets are original teaching material. Further reading supplies professional background; local conventions are stated explicitly.