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.
Several metrics are related such as the following below. You should be able to calculate all of them as preparation for a Six Sigma certification exam.
TOP - Total Opportunities
DPU - Defects Per Unit
DPMO - Defects Per Million Opportunities
Click here to get a DPMO and Six Sigma Calculator that also computes DPO and DPU and allows you to analyze various scenarios and the impact on the metrics.
Six Sigma Modules
The following are available
Green Belt Program (1,000+ Slides)
Cost of Quality
Cause & Effect Matrix
Central Limit Theorem
Correlation and Regression
MTBF and MTTR
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