in order to move from ML3 to ML4 we have understood that processes selected for OPP must be all the processes the organization has to statistically measure in order to reach its business goals. Is it right or there is a minimum set of processes to select for OPP that is judged adequate for a ML4?
Please another two questions:
- do you think using Six-Sigma is necessary in order to move from ML3 to ML4?
- do you think a 20-months PI project is too long in order to move from ML3 to ML4 for a large organization (1000)?
Hmmmm.....interesting question. Since the inception of so-called "high-maturity" people have been struggling with this. How many is enough? What are the right sub-processes to analyze? What will a Lead Appraiser and the SEI "accept?" The answer that has been broadcasted loud-and-clear by the SEI is "it depends!"
As frustrating as that is for most people, I've come to be comfortable with it (I have not always had this opinion btw).
This is one reason you should avoid hiring a cheap Lead Appraiser last minute for the minimum amount of days, because his/her perception of your organization's needs, goals, objectives, and behaviors is critical to helping to lead a team through that judgement call.
It really does come down to how you are running your business, and is the process you are using, and the data you are collecting, really credible.
I always tell my clients they should focus on "being a great company" and stop worrying about CMMI. If they focus on that, they WILL reach their CMMI goals - but usually not without some honest self-evaluation and hard work.
If you build static web pages in a small-setting for a living, the number of sub-process that are being statistically managed might be small - say 3-4. If you're building the Atlas rocket for NASA with 5000 engineers, you probably have a lot more - possibly 20 or 30. It's all about context, goals, objectives, strategy, risk, and customer satisfaction.
Your best bet is to engage a Lead Appraiser who really understands your business model, knows you well, and who can help you make an informed choice.
As to your other questions, Six Sigma certainly can HELP you in your quest to become a great company through the use of statistical analyses and methods, but it's not required. Six Sigma brings some structure to the process that may not exist, but it's only one answer.
I can't really address the timing issue - 20 months seems credible, but without knowing more about your organization it's really hard to say. Take a look at the "Time to Move Up" chart I posted a few days ago from the SEI. It's an analysis of what other companies have done.