What is the conversion for PPM defects vs. Sigma Equivalents?

S

sixsigmais

Just use the excel formula
=(1-NORMDIST(sigma-1.5,0,1,1))*1000000

Replace the sigma with the number of sigma you like to find.

So, 6 sigma
=(1-NORMDIST(6-1.5,0,1,1))*1000000 = 3.4ppm

5 sigma
=(1-NORMDIST(5-1.5,0,1,1))*1000000 = 233ppm

and so on

P

Palt88

Just use the excel formula
=(1-NORMDIST(sigma-1.5,0,1,1))*1000000

Replace the sigma with the number of sigma you like to find.

So, 6 sigma
=(1-NORMDIST(6-1.5,0,1,1))*1000000 = 3.4ppm

5 sigma
=(1-NORMDIST(5-1.5,0,1,1))*1000000 = 233ppm

and so on
Thanks

But I'm looking for the "unshifted" one...
Usefull anyway!

Do someone got a statistical software (else than minitab) to check what level of total ppm it gives with a sigma level of 4.5 ???

A

Al Hector

But I'm looking for the "unshifted" one...
Usefull anyway!

Do someone got a statistical software (else than minitab) to check what level of total ppm it gives with a sigma level of 4.5 ???
I am not very familiar with this subject, but after a quick search I found something that maybe is useful for you : there is a tabel which can be downloaded from the following link :

Alin

S

sixsigmais

Thanks

But I'm looking for the "unshifted" one...
Usefull anyway!

Do someone got a statistical software (else than minitab) to check what level of total ppm it gives with a sigma level of 4.5 ???
Just modify the formula to
=(1-NORMDIST(sigma,0,1,1))*1000000

Then the ppm is "unshifted"
For 4.5 sigma (unshifted), it is 3.4ppm

P

Palt88

Sixsigmais: Thanks for the formulas. I have also modified the shifted fbut I make the error to multiply the result by 2, which makes me confused.

The unshifted formula gives exactly the same results provided by a statistical software.

But still confused why the ppm level is doubled (excep at 4.5 sigma) in the previous unshifted tables....thing that I'm unable to simulate with a statistical software even with a centered double sided distribution...

Tim Folkerts

Super Moderator
The tables seem to be full of mistakes, so don't worry too much about them.

Products can be above spec of below spec. In principle you should calculate the upper and lower tail for every case. However, when one tail is farther from the center than the other, then the far tail can typically be ignored.

Attached is a simple spreadsheet with sigma levels, defects in the close tail, the far tail, and total defects. You can set the shift to see how many defects are in each tail. For SHIFT = 0 you get the traditional values. For SHIFT = 1.5 you get the "Six Sigma" values. Even SHIFT = 0.1 will make the close tail considerably bigger than the far tail.

Tim

Attachments

• 10.5 KB Views: 473
B

Bheemaraj

Please see attached six sigma spreadsheets. Sigma to ppm worksheet (PPM). Create your own chart by typing in numbers.

Attachments

• 287 KB Views: 425
• 17.5 KB Views: 355

Stijloor

Staff member
Super Moderator
The tables seem to be full of mistakes, so don't worry too much about them. <snip>
Tim, what is your view of the 1.5 sigma shift?

mdurivage

Quite Involved in Discussions
Here is a little cheat sheet that I use.

Attachments

• 24.4 KB Views: 289

GManikandan

Registered
Re: Thank you all.

I'm thoroughly impressed. I've looked for this conversion on and off over the years. I even asked a professor from a college in Dayton and he could only quote the emperical rule. Thank you for your help. I only hope that I can help someone else someday.

Totumfrog
Hello Tm Folkerts, D.Scott, Totumfrog,

Can you please post the Z table which you have used in the above explanation?

Thanks
G.Manikandan

Conversion of coordinate dimension holes to position dimension Design and Development of Products and Processes 3
MDD to MDR - Technical File conversion EU Medical Device Regulations 4
Class II to OTC conversion of a medical device 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 1
How do you manage your project? Data Conversion and Digitization Records and Data - Quality, Legal and Other Evidence 9
Surface Roughness - Conversion of RS on a Print to RZ General Measurement Device and Calibration Topics 3
P Conversion of fraction to decimal for R&R of english ruler Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 8
P Effective way for DC/DC conversion for 2 MOPP @ 250VAC IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
Conversion and Rounding Standard for converting metric to english and vice versa Other ISO and International Standards and European Regulations 4
P IEC 60601-1-11 - Conversion to Double Insulation IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
M Customer Conversion and Retention / Satisfaction Measurement Index Benchmarking 4
S Quality Objectives for Aerospace Chemical Conversion & other Surface Treatment Plant AS9100, IAQG 9100, Nadcap and related Aerospace Standards and Requirements 3
B QMS Conversion including Documentation and Understanding our Processes ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 3
R Preparation for AS9100B conversion to AS9100C AS9100, IAQG 9100, Nadcap and related Aerospace Standards and Requirements 5
S FSC Chain of Custody - Volume Control & Conversion Factors Various Other Specifications, Standards, and related Requirements 7
S Surface Finish - Conversion factor to transform Rz Jis in Rz Inspection, Prints (Drawings), Testing, Sampling and Related Topics 6
T Specification Conversion from Sets to Individual Measurements? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 5
F Conversion from Agile - Need cheaper FDA compliant software Qualification and Validation (including 21 CFR Part 11) 7
C Conversion Help!! Print with this dimension .2917+/-.0005 :1 Inspection, Prints (Drawings), Testing, Sampling and Related Topics 9
Unit Conversion Add-in for Excel Excel .xls Spreadsheet Templates and Tools 7
I Medical Device Directive, Conversion from class IIb to class III EU Medical Device Regulations 4
A CMM Software Conversion - Converting from Zeiss/Calypso to Brown & sharpe PCDMIS Inspection, Prints (Drawings), Testing, Sampling and Related Topics 7
K Micron to Inch Conversion Misc. Quality Assurance and Business Systems Related Topics 10
P Rockwell, Brinell, Vickers Conversion - Evaluating Aluminum 6061-T6 and 6063-T6 General Measurement Device and Calibration Topics 11
E Cost Savings based on 2005 Production - Metric Conversion Problem Misc. Quality Assurance and Business Systems Related Topics 4
Conversion of surface finish measurements Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4
Microfinish conversion - Micrometers (?) to microinches? Manufacturing and Related Processes 3
Conversion TO ISO9001:2000 / TS16949:2002E IATF 16949 - Automotive Quality Systems Standard 7
K Conversion from ISO 9001:1994 to ISO 13485:2003 ISO 13485:2016 - Medical Device Quality Management Systems 4
I ISO 9000:2000 Conversion Presentation Request ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 1
Best 'Units' Conversion Web Site and/or Program Book, Video, Blog and Web Site Reviews and Recommendations 6
S Conversion from ISO 9001:1994 to 9001:2000 ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 3
Targets / limits for PPM/ Scrap Manufacturing and Related Processes 2
Internal PPM Manufacturing and Related Processes 1
ISO 2859-1 - 9.3.3.2 Switching score - Sampling Plans and PPM AQL - Acceptable Quality Level 0
Software for Supplier Charge back and internal PPM General Information Resources 2
PPM - wrong parts or defective parts? IATF 16949 - Automotive Quality Systems Standard 18
PPM calculation of customer complaints for PMS Customer Complaints 10
Determining what type of scrap to include in my internal PPM calculation Quality Manager and Management Related Issues 5
PPM, Pictorial Process Mapping, Templates Manufacturing and Related Processes 5
PPM - Internal PPM / External PPM Quality Manager and Management Related Issues 4
PPM Defect Rate as a Performance Metric - Are there Flaws? Quality Manager and Management Related Issues 9
Converting ETO Residual Limits from PPM to mg ISO 13485:2016 - Medical Device Quality Management Systems 6
Internal PPM's in a medium sized metal stamping plant Quality Manager and Management Related Issues 6
S What is appropriate PPM level for a Plastic Injection Moulding Supplier Quality Tools, Improvement and Analysis 4
PPM - Filtering Defects out of calculation Quality Tools, Improvement and Analysis 5
Is PPM a good metric for gathering companywide complaints ? Customer Complaints 2
L Oil Field Bearing Production PPM Standard Benchmarking 2
How is PPM (Parts Per Million) Calculated? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4
L Help with concept of PPM in SPC Statistical Analysis Tools, Techniques and SPC 6
Z Predicting External PPM Capability from Internal PPM Capability, Accuracy and Stability - Processes, Machines, etc. 1