◉ A Six Sigma defect is defined as anything outside of customer specifications.
◉ A Six Sigma opportunity is the total quantity of chances for a defect.
This chapter provides a list formulae normally used to measure different metrics related to Six Sigma defects.
Defects Per Unit - DPU
Total Number of Defects
DPU = ------------------------
Total number of Product Units
The probability of getting 'r' defects in a sample having a given DPU rate can be predicted with the Poisson Distribution.
Total Opportunities - TO
TO = Total number of Product Units x Opportunities
Defects Per Opportunity - DPO
Total Number of Defects
DPO = ------------------------
Total Opportunity
Defects Per Million Opportunities - DPMO
DPMO = DPO x 1,000,000
Defects Per Million Opportunities or DPMO can be then converted to sigma values using Yield to Sigma Conversion Table given in Six Sigma - Measure Phase.
According to the conversion table:
6 Sigma = 3.4 DPMO
How to find your Sigma Level
◉ Clearly define the customer's explicit requirements.
◉ Count the number of defects that occur.
◉ Determine the yield-percentage of items without defects.
◉ Use the conversion chart to determine DPMO and Sigma Level.
Simplified Sigma Conversion Table
| If your yield is | Your DPMO is | Your Sigma is |
| 30.9% | 690,000 | 1.0 |
| 62.9% | 308,000 | 2.0 |
| 93.3 | 66,800 | 3.0 |
| 99.4 | 6,210 | 4.0 |
| 99.98 | 320 | 5.0 |
| 99.9997 | 3.4 | 6.0 |
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