How it works
DPMO scales the number of defects to one million opportunities, so products of different complexity can be compared. The sigma level includes the conventional 1.5σ long-term shift used in Six Sigma tables: 3.4 DPMO corresponds to 6σ.
Formula
DPU = defects / units DPMO = defects / (units × opportunities) × 10⁶ σ = Φ⁻¹(1 − DPMO/10⁶) + 1.5
An opportunity is a characteristic that can go wrong and can be checked, such as a solder joint or a drilled hole. If you only judge each unit as good or bad, use one opportunity per unit; DPMO is then equal to ppm.
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