01 · Purpose
Why and when to use it
Use it to quantify the gap agreed in Define and create a comparable reference for later improvement.
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.
- Select output and guardrail measures from agreed requirements.
- Validate definitions, sources and measurement suitability.
- Collect representative data and record exclusions.
- Report rates with counts, denominators, period and relevant groups.
- Inspect stability and uncertainty before extrapolating or comparing periods.
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.
| Baseline measure | Illustrative result |
|---|---|
| Late dispatch | 180 of 1,000 eligible orders = 18% |
| Order accuracy | 970 of 1,000 orders correct = 97% |
| Missing handover records | 20 additional cases; shown separately from the 1,000 known cases |
04 · Interpretation
What the result tells you
The 18% is a known-case rate. If the 20 unknown cases belong to the same eligible population, the full rate lies between 180/1,020 = 17.65% and 200/1,020 = 19.61%, depending on their status.
Completion check: A trustworthy performance baseline with coverage, uncertainty and guardrails.
05 · Judgement
Mistakes and limitations
Changing definitions, product mix or sampling can create apparent improvement. Overall performance indices Pp/Ppk use overall spread; they are distinct from Cp/Cpk with an appropriate within-process sigma estimate.
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.