DPMO is a process performance measurement which stands for Defects Per Million Opportunities. It predicts how many defects will occur over the next million opportunities based on the sample analysed.
A process which has 3.4 DPMO has achieved a Six Sigma level of operation, this is near perfection. Most processes operate at a 3 sigma level which is 66,807 DPMO.
To understand DPMO you first need to understand the difference between a “defect” and something that is “defective”. A defect is a non-conformance or error which has occurred in a unit (often a product product or service), there could be multiple defects in one unit. Defective refers to a unit which contains one or more defects.
Example: An application form (the unit) could have 5 fields to complete. Each field is an opportunity to make a mistake (a defect) and if any filed is missed or not completed correctly the form becomes defective. In this example the form could have 1-5 defects, but no mater how many there are the form is still defective.
So with that in mind, DPMO tells us out of 1 million opportunities to make a defect how many defects will occur (based on the data provided to make the calculation).
Number of defects identified
(number of units X defect opportunities per unit)
Formula in simple terms
Divide the total number of defects found by the total number of defect opportunities in the sample (number of units X number of defect opportunities per unit = total number of defect opportunities in the sample).
An application form has 5 fields which the applicant must complete. Each of these fields are an opportunity to make a defect.
30 applications are returned and 4 are defective. When we look at the defective applications we find the following:
|Application No.||No. of Defects|
Total number of defects 8 / total opportunities to make a defect (30 x 5) 150 x 1,000,000 = DPMO 53,333
In this example we have calculated that for every million opportunities to make a defect 53,333 defects will occur. This is a sigma level of 3.1 which is about average.