# Six Sigma - Defect Metrics

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Before we go ahead, let us 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.

This chapter provides a list formulae normally used 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 |

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