Defects per Opportunity is the probability of units produced with zero defects by the process. One part (or unit) may have as low as one opportunity for a defect or it may have infinite opportunities for defects.
A complex stamping for an airplane fuselage may have hundreds of characteristics that can each be defective. If any one of those characteristics is out of specification (aka there is a defect) then the unit is considered defective. A simpler product such as nail will have fewer opportunities. Measurable opportunities are considered.
D: # of defects
O: # of opportunities for a defect
U: # of units
TOP: Total number of opportunities = U * O
Examine the table shown below:
D = 19 defects
O = 5 opportunities
U = 10 nails
TOP = 50 total opportunities
DPU = 1.9 defects per unit
DPO = 0.38 defects per opportunity.
Each opportunity (length, diameter, plating, hardness, material) has an average of 0.38 defects in each nail.
Notice below that only 2 nails of the 10 total nails were completely defect-free and 8 of the nails were defective....meaning that each of the 8 nails had at least one type of defect. That means the PPM is 8/10 or 800,000.
DPMO and PPM can be different values. Click here to learn more.
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