# Six Sigma - Defect Metrics

Before we go ahead, lets define two terms:

A Six Sigma defect is defined as anything outside of customer specifications.

A Six Sigma opportunity is the total quantity of chances for a defect.

Here are various formulae to measure different metrics related to Six Sigma Defects

## Defects Per Unit - DPU

Total Number of Defects DPU = ------------------------ 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

Total Number of Defects DPO = ------------------------ 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

If your yield is: Your DPMO is: Your Sigma is: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