Hi All,

Can anybody explain me wht is the difference between PPM & DPMO

if u have example pls enclosed with the answer

Dear Guru Prasad,

I have seen PPM (Parts per Million) used in the context of defectives where the entire product or service is defective. So, if we make 100 TVs and out of which 4 are defective then PPM = 40,000. The Opportunities per Unit (OFE) = 1 in this case. PPM is used when expressing the same as a percentage is not convenient. For example, if we say we had 0.0004% defective, then it is hard for us to gage or work with this value, so it becomes easier to look in terms of PPM (4).

DPMO (Defects per Million Opportunities) is used in the context of defects where a product can have one or more defects. So, if we make 100 TVs and there are 40 defects in total, then DPMO = 400,000.

Both PPM and DPMO refer to a base of Million (1,000,000). Sometimes, they are used interchangeably.

SJ

SJ,

Does that mean, if only defective is known, it is assumed that defect per defective = 1?

Hi Shalini,

I do not think that if count of defectives is known, it makes defects per defective is 1. 1 Defect could also result in a Defective and >1 defect also could result in Defective.

The Defects/Defective needs to be measured seperately if that is of interest.

Hope it helps..

Kiran Varri

Dear Kiran/Shalini,

Both of you are right.

If both are known, then we usually work with the defects and if we drive the defects down the zero, then defective also goes down to zero.

However, if we are working with only defectives, some people assume defects = defectives. As Kiran points out, technically, they are different.  Please note that there are some practitioners who believe that we should only be working with defectives and not defects because we may artificially claim a good process sigma level if we inflate the number of possible  defects in a product/service.

Best Regards,

SJ

.....measure defectives from DPMO? because I'm fully aligned with what Kiarn has pointed out that a defective product can have many defects! and by assuming defect = defective by some people (as mentioned by SJ) then there is also a risk of deflating the sigma value of the process! The process might not be that poor as sigma value w'ld indicate.

Coming back to my query:

For eg if DPMO = 20000 (known) and the process is worked on defectives then is the question framed correctly or its being assumed that in absence of defects, DPMO can also stand for Defectives Per Million Opportunity?

Tks,

Shalini