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Converting DPMO & Sigma Level

07/27/2007

How do you covert DPMO to sigma level and sigma level to DPMO?
Al F.

Generally, you would use a table, such as provided in my
Six Sigma Demystified book (see below), or you can calculate it directly in Excel using the formula =(NORMSINV(1-$D2))+1.5, where the data in cell D2 is entered as a decimal (for example, 30% error rate = 300,000 DPMO = 0.3 which calculates as 2.02 Sigma Level).

 

For a given sigma level, the defects per million opportunities (DPMO) is provided, assuming normality and a 1.5 sigma shift. Note that below approximately 3 sigma defects are included from both tails of the normal distribution.

Sigma

DPMO

1

697672

1.1

660083

1.2

621378

1.3

581815

1.4

541694

1.5

501350

1.6

461140

1.7

421428

1.8

382572

1.9

344915

2

308770

2.1

274412

2.2

242071

2.3

211928

2.4

184108

2.5

158687

2.6

135687

2.7

115083

2.8

96809

2.9

80762

3

66811

3.1

54801

3.2

44567

3.3

35931

3.4

28717

3.5

22750

3.6

17865

3.7

13903

3.8

10724

3.9

8198

4

6210

4.1

4661

4.2

3467

4.3

2555

4.4

1866

4.5

1350

4.6

968

4.7

687

4.8

483

4.9

337

5

233

5.1

159

5.2

108

5.3

72

5.4

48

5.5

32

5.6

21

5.7

13

5.8

9

5.9

5

6

3.4

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