01 · Purpose
Why and when to use it
Use it to inspect distribution shape and spread when there are enough observations to make grouping useful.
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.
- Check units, missingness and whether distinct process groups should be separated.
- Choose interval boundaries and a clear boundary convention.
- Count observations in each interval.
- Use adjacent bars; for unequal widths use density so area represents frequency.
- Compare alternative sensible bin widths and avoid declaring a distribution from shape alone.
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.
| Packing-time interval (minutes) | Count in illustrative sample |
|---|---|
| 0 ≤ x < 5 | 3 |
| 5 ≤ x < 10 | 2 |
04 · Interpretation
What the result tells you
The sample 2, 4, 4, 6, 9 gives three observations below five and two from five to below ten. Five observations are too few for a reliable judgement about distribution shape.
Completion check: A numerical distribution display with explicit interval rules and contextual interpretation.
05 · Judgement
Mistakes and limitations
A bell-shaped histogram does not prove normality, stability or independence. Pooling shifts or products can create misleading mixtures.
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.