01 · Purpose
Why and when to use it
Use it to explore potential relationships and generate questions for Analyze, without treating association as proof of causation.
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 two numerical variables and the pairing rule.
- Check units, missing pairs and time alignment.
- Plot each pair with labelled axes.
- Inspect shape, groups and influential observations.
- Consider confounding and time effects before choosing further analysis.
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.
| Order | Lines in order | Packing time (minutes) |
|---|---|---|
| A | 1 | 3 |
| B | 3 | 5 |
| C | 5 | 9 |
| D | 7 | 10 |
04 · Interpretation
What the result tells you
Packing time rises with line count in these four fictional pairs. The plot cannot establish that line count alone explains the difference; item size, staff and workload may also matter.
Completion check: A paired-variable plot with a context-aware description of association.
05 · Judgement
Mistakes and limitations
Pairing unrelated observations creates meaningless results. A weak linear pattern can conceal a curved relationship; grouping can change the apparent association.
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.