Metrics of Six Sigma

Metrics of Six Sigma

Six Sigma is a business process improvement methodology that is widely used in almost every industrial sector. Six Sigma makes improvements with the help of data. The data-driven methodology gives the business to make decisions more effectively. Data forms the foundation of the Six Sigma management systems. The metrics that are derived from the data help businesses’ to make decisions on the processes. The metrics are defined into two as Primary metrics and secondary metrics. 

Primary Metric:

The Primary Metric of six sigma is a generic measure of project success. It is defined by Project champion, Sponsor, Black belt or Green Belt. Primary Metric should be checked at the end of the Six Sigma improvement project to track the progress. It defines the success of the six sigma project. Any six sigma project must set the primary metric before starting the project. 

The primary metric should be: 

  • Aligned with the problem statement 

  • Measurable 

  • Aligned with business objectives 

  • Measured in the proper frequency 

The primary metric is the indicator of a project which is an important parameter to measure the success of the project. But it should not make the practitioners lose focus on secondary metrics. As much as the primary metric, a secondary metric is also important. 

Secondary Metric: 

The secondary metric is the thing that businesses cannot afford to lose while improving the primary metric of the business process. A secondary metric is the one which helps a business to makes sure that their problems are not changing forms or changing faces. The secondary metric helps the business to do the improvement process honestly. The secondary measure also should be measurable in terms of quality. 

Example: If you’re starting the six sigma project for saving energy in your office, then energy consumption is your primary metric. To reduce energy consumption, you can decide to turn off A/C system but that will reduce the comfort of the office worker. You can’t afford to lose comfort. So, Comfort is your secondary metric of the project. 

Some Common Metrics:

Other than Primary and secondary metrics some common metrics that are used in the six sigma are as follows


DPO stands for Defects Per Opportunity. It is the ratio between the number of defects and the total number of defect opportunities in the sample. 

For Example, the number of defects that can occur in a shoe is 4 such as miss-stitches, incorrect sole, color mismatch, size difference. If the defects are measured in the 100 shoes,  total opportunities for defects are 400. Out of which there are 3 incorrect soles and 5 color mismatch. 

Hence, DPO = 8/400 


DPU stands for Defects Per Unit. It differs from DPO in a way that DPO deals with opportunities in the product whereas DPU deals with the defective product itself. In the above example, if those defects are found only in 4 shoes out of 100. 

DPU = 4/100 


DPMO stands for Defects per Million Opportunities. It is the measure of defects in million opportunities. It is an important measure of the sigma level of the company. Sigma level of the company is decided in with help of DPMO. 3.4 DPMO means a company is operating in Six sigma level. 

DPMO = DPO x 1,000,000 
            = 8/400 * 1000000 
            = 20000 

There are a lot of metrics to look after in the six sigma project. Six Sigma practitioners must define their primary and secondary metrics clearly. So that their project can be tracked in terms of metrics. Common metrics are used in the case of most manufacturing industries, pharmaceutical industries and the food industry where they deal with defects. So these industries can use these common measures to track their performance.



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