What data do you need?
Collect defect counts, inspected units and the number of defined defect opportunities per unit. A unit can contain multiple defects. For mixed products, sum the actual opportunities rather than assuming the same count for every unit.
Worked example
For 40 defects in 2,000 inspected units with 5 opportunities per unit, DPMO = 40 / (2,000 × 5) × 1,000,000 = 4,000. DPU = 40 / 2,000 = 0.02 defects per unit. Neither metric by itself tells you the percentage of defective units.
How to use this Six Sigma tool
- Define a defect and each opportunity before collecting data.
- Open defect analysis and enter consistent counts and opportunities.
- Use defect categories and Pareto analysis to prioritize investigation.
How to interpret the results
The DataStatPro defect tool groups defects and reports DPMO and a threshold-based sigma estimate. Treat sigma levels as approximate categories. Do not present that estimate as an exact inverse-normal conversion; sigma conventions, including a 1.5-sigma shift, must be stated explicitly.
Are DPMO and PPM the same?
DPMO counts defects relative to defect opportunities. Defective-unit PPM counts defective units relative to inspected units. They coincide only under compatible definitions, such as one opportunity per unit and at most one defect per unit.