Lets define two terms before going forward:
- In Six Sigma, a defect is defined as anything outside of customer specifications.
- In Six Sigma, an opportunity is the total quantity of chances for a defect.
Defects Per Unit (DPU):
DPU = (total number of defects)/(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):
DPO = (total number of defects)/ (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
Yield DPMO Sigma
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
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
Six Sigma - Summary
- Six Sigma is a philosophy of quality improvement.
- Six Sigma is 3.4 defects in one million opportunities (DPMO).
- Components of Six Sigma are Customer, Process, and Employees.
- Six Sigma implementation requires the following roles:
- Business Leader
- Sponsor
- Black Belt
- Master Black Belt
- Green Belt
- The generic cycle of Six Sigma includes the following phases: Define, Measure, Analyze, Improve, and Control.
- Six Sigma is dedicated to 'Customer focus'.
