01 · Purpose
Why and when to use it
Use sampling when a census is impractical, costly or destructive, or when representative coverage matters more than raw volume.
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.
- Define the population, period and unit of observation.
- Identify a usable sampling frame and relevant groups.
- Choose random, stratified or another defensible selection method.
- Determine size from the estimation goal, precision, variation and practical constraints.
- Record selection and non-response; preserve time order where stability will be assessed.
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.
| Design decision | Example |
|---|---|
| Population | All standard orders released over four weeks |
| Coverage | Both shifts, weekdays and peak demand |
| Selection | Random orders within shift strata |
| Aggregation | Weight strata appropriately if their sample shares differ from population shares |
04 · Interpretation
What the result tells you
Equal samples from two shifts do not represent their combined error rate equally if one shift handles most orders. Report the sampling design with the estimate.
Completion check: A justified sampling design with coverage, size rationale and selection records.
05 · Judgement
Mistakes and limitations
Avoid universal sample-size rules. Systematic sampling may align with a process cycle; clustered cases may be dependent. Confidence calculations must match the design.
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.