01 · Purpose
Why and when to use it
Use it to describe defect burden per order, product or another defined unit.
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 unit and distinct defects.
- Specify whether repeated occurrences of one defect type count separately.
- Record all eligible units and their defects.
- Divide total defects by total units.
- Report the counting rules and the distribution of defects across units when useful.
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.
| Illustrative record | Result |
|---|---|
| 100 orders inspected | 12 defects across 8 nonconforming orders |
| DPU | 12 / 100 = 0.12 defects/order |
| Nonconforming fraction | 8 / 100 = 8%; not 12% |
04 · Interpretation
What the result tells you
DPU of 0.12 does not tell us exactly how many units are defect-free without unit-level records. Estimating yield as exp(−DPU) requires a suitable Poisson model; it is not an identity.
Completion check: A defect-per-unit measure with consistent counting rules.
05 · Judgement
Mistakes and limitations
Changes to what counts as a defect can change DPU without changing the process. Exposure varies when units differ greatly in size or complexity; consider that before comparing.
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.