Defects Per Million Opportunities (DPMO)

To achieve Six Sigma quality, a process must produce no more that 3.4 defects per million opportunities. An opportunity is defined as a chance for non-conformance or not meet­ing the required specifications. This means one needs to be nearly flawless in executing key processes. The process and culture is conditioned for zero defects rather than being one that accepts that it is inevitable, and acceptable that mistakes will occur.

Hence, Six Sigma delivers substantial cost reductions, enhanced efficiencies, sustainable improvement and increased stakeholder value.

A defect is defined as any part of a product or service that does not meet customer specifications or requirements or causes customer dissatisfaction or does not fulfill the func­tional or physical requirements. It should be noted that the term customer refers to both internal and external customers.

Opportunities are the total number of chances per unit to exhibit a defect. Each opportu­nity must be independent of other opportunities and must be measurable and observable. The final requirement of an opportunity is that it directly relates to the CTQ. The total count of opportunities indicate the complexity of a product or service.

A unit is something that can be quantified by a customer. It is a measurable and observ­able output of the business process. It may manifest itself as a physical unit. In case of a service, it may have specific start and stop points.

Defects per unit (DPU) are defined as the number of defects in a given unit of product or process.

Defects per million opportunities (DPMO) are calculated as:

There may be different approaches to calculate the sigma level of the processes. Table 7.3 shows the sigma levels for various DPMO.

Example 1:

A purchase order has 50 opportunities for errors. The operator who enters data to prepare the purchase order makes one defect on an average. The DPMO in this case will be:

Example 2:

Area: Receptionist attending to phone calls for a company.

Customer complaint: “I have to generally wait too long to speak to a representative in this company.”

CTQ name: Responsiveness of the receptionist.

CTQ measure: Time on hold (seconds).

CTQ specification: Less than 60 seconds from call connection to the automated response system.

Defect: Telephone calls with hold-time equal to or greater than 60 seconds Unit: A telephone call.

Opportunities of defects per unit: 1 per call.

Number of defects: 99 telephone calls.

Total number ofunits (calls) in the duration considered: 1,482 calls.

Source: Poornima M. Charantimath (2017), Total Quality Management, Pearson; 3rd edition.

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