Re: DPPM - quality indicator?
I use both (i.e. the different between DPPM and DPMO is just the "O"). Lets look at the definition and it will become clear:
DPMO = 1M * [D / (N*O)]
D= Total number of defects counted in the sample
N= Number of units of product or service
O= Number of opportunities per unit of product or service
1M= One million
Note: Just make the O=1 and your are back to DPPM.
The question is: what do you want to see?
a) The proportion of defective units with respect to your sample
b) The proportion of defects with respect all the opportunities within your sample
In practice: Companies use both for internal analysis but typically disclose only one (DPPM) in order to provide the customer with a number that is easier to understand.
DPMO=3.4 corespont to a sigma level of 6, and a yield higher than 99.99%
DPMO=233 -> 5 sigma, yield 99.98%
DMPO=6,210 - 4 sigma, Yield 99.4%
Last edited by cuadra - 2010; 8th December 2006 at 04:57 PM.