DPMO and Sigma Level

Questions are never Stupid.
Yes ! Answering can be in a Stupid ways

Hi Straydog,

Thanks for your reply. It clarifies DPMO , DPMU but it raises one more question.
Customer is interested in DPMU which means Sigma Level should be measure at the Last Process Step.

Which makes it similar to RTY.
That means in a 10-Stage process each prior stage should be greater than 6-Sigma level.

End product to customer is combination of many set of products. e.g. TV+Remote.
So if TV & Remote assembly line produces 6-Sigma Level,
Then the final sigma level to customer would be ADDITIVE or MULTIPLICATIVE of both these Sigma levels

Awaiting you reply.

There’s a reasonable assumption that reducing DPMO must also reduce DPMU. You may not be able to say whether it’s additive or multiplicative since mulitple defects may appear in a single unit (DPU). If you yave 3 delivered defects you could have anywhere from 1 to 3 defective units. If you really want to understand the 6s-DPMO metric, pick up Armand Feigenbaum’s book “Total Quality Contol”. For a criticism on whether it makes sense see Arthur M. Schneiderman’s posted article: http://www.schneiderman.com/The_Art_of_PM/six_sigma_metric/six_sigma_metric.htm
I emphasize customer focussed metrics. In the end, all internally focussed metrics are delusional if they differ from what the customer is seeing. From your original question I can guess that this is also your concern. Cheers.

Man you recommend boring reading.

Focusing solely on customer metrics is delusional. It is driving looking only at your rear view mirror. The data is slow and unreliable.

The reason for the internal focus is to have a more timely indicator. The things you see in your operation are the things your customer sees. You balance this by making sure that as you drive internal metrics the external metrics follow (but lag).

It’s QTC – Quality, time and cost.

Internal quality – DPMO
External quality – returns and complaints

Internal time – cycle time
External time – delivery complete to customer’s requested time

Cost is total cost – you have to comprehend the entire value chain

Stan, thanks for contributing your wisdom. I actually agree with you and I apologize to anyone else who may have thought I was recommending DPMU over DPMO. Complaints about delivered defects/defectives only tell us that something is wrong. The quandry in the original post was that there can be a disconnect between our internal quality metrics and what the customer sees — the point that Schneiderman makes and explains in his article. So let’s accept that 6s based on DPMO may not mean that the customer is seeing that level of quality and listen to VOC to tell us we still need to do better.

I’m a new subscriber to iSixSigma. Would like to read the original article. Where is this, and other articles, published?