Six Sigma was invented to improve the manufacturing processes and it aims to improve the process output through various techniques which involve removal of errors and reduction of variable quotient in business and manufacturing processes.
Six Sigma levels represent the reliability of the process, higher Six Sigma means the process is reliable and working in good condition. Let us assume, if Six Sigma level one means 61% of the parts produced or service rendered by the process are defective, which further means only .00034 percent of the parts are defective. The Six Sigma is calculated by the number of defects per million opportunities (DPMO).
The sigma level provides the metrics to understand the capability of the process or an organization to meet the customer requirements.
When DPMO is calculated?
- DPMO is calculated in the measure phase of the DMAIC Process, DMAIC Define, Measure, Analyze, Improve and Control. It refers to a data driven quality strategy for improving processes.
- DPMO may be used throughout in the DMAIC process as per the questions raised.
- It is calculated to improve the Six Sigma phase.
How to calculate DPMO?
DPMO can be calculated by gathering the information. First we have to collect the data for the number of units produced, the number of defect opportunities per unit and the number of defects.
The below mentioned formula to calculate the number of defects in the process per million opportunities;
DPMO is number of Defects x 1,000,000((Number of Defect Opportunities/Unit) x Number of Units)
Let’s brief it through the example of Laptop manufacturer who wants to calculate the Six Sigma of its manufacturing process. For two months, the manufacturer makes 83,934 laptops and during the test phase, 3,432 laptops were rejected.
From the above mentioned formula, we get defects = 3432 Opportunities = 83934 Defect Opportunities per unit = 9 DPMO = 5111.158768
You can use the Six Sigma table below to find out the level for respective DPMO value:
Six Sigma Level DPMO 1 690,000 2 308,000 3 66,800 4 6,210 5 320 6 3.4 For the example given above, DPMO of 5,111 is less than 6,210 and greater than 320. Hence, it results in a Six Sigma level four designation.
Six Sigma calculations are all about statistical analysis and report generation through which anyone can understand the process flaws and requirements. Through the above mentioned examples, you can calculate Six Sigma to a wider level.