01 · Purpose
Why and when to use it
Use it to describe average performance and support analyses whose assumptions make the mean relevant.
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, eligible observations and missing values.
- Add the observations.
- Divide by the number of included observations.
- Report the unit, sample size and period.
- Compare the mean with the distribution, median and time behaviour.
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.
| Calculation for 2, 4, 4, 6, 9 minutes | Result |
|---|---|
| Sum / count | 25 / 5 |
| Mean | 5 minutes |
| If 9 is replaced by 29 | 45 / 5 = 9 minutes |
04 · Interpretation
What the result tells you
A single larger observation moves the mean substantially. Whether that observation is valid must be investigated rather than decided by its effect on the average.
Completion check: A correctly calculated mean with units, coverage and distribution context.
05 · Judgement
Mistakes and limitations
The average alone hides spread, tails and instability. Averaging subgroup means without weighting can distort a combined mean when subgroup sizes differ.
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.