Process Capability Cpk, Workout, & Witch Hunts

Update: To read Craig Gygi’s responses, visit these two posts:

1. Original Questions posed to Craig Gygi
2. Craig Gygi answers Question on Process Capability
3. Craig Gygi answers Question on Accelerated Life Testing

On May 25, I announced a contest whereby the readers of shmula could enter and win a Six Sigma for Dummies Workbook.  In the proceeding posts, I’ll be posting Craig Cygi’s responses to those questions.  Today are Craig’s response to the question on the Process Capability Index (C_pk) as a measurement for Process Capability, thoughts on introducing Lean and Six Sigma into an organization, and some comments around the recent cynicism toward Six Sigma.

Some background first on the contest and to view the winners, please go here:

Below were the contest details:

Submit your Six Sigma questions and enter a chance to win Six Sigma Workbook For Dummies, an industry bestseller since its publication in 2005.  We are fortunate to have Craig Gygi, the lead author of Six Sigma for Dummies and the companion Six Sigma Workbook For Dummies to answer reader’s questions for this raffle.

To enter,

1. Submit your question for Craig in the comments of this post.
2. Comments will be turned off on June 8, 2007
3. We will enter all the commentators names on my handy-dandy randomizer, using a hard-to-crack random seed, and 5 randomly selected contestants will win a Six Sigma Workbook For Dummies book.
4. On June 11, 12, 13, 14, and 15, I will publish Craig’s answers to some or all of the reader’s questions.
5. That’s it.

Process Capability Cpk Index

Gary Petersen said,
May 25, 2007 @ 3:20 pm

Assuming that I have an in-control, steady process and a reasonable measurement system, is Cpk the best way to measure process capability? Or are there other statistically valid ways to do this?

C_pk is ideal for quickly measuring or communicating a single, overall metric that describes the capability of a process.  But yes, there are other valid ways of assessing process capability.  What is best depends on the situation.  For example, another condensed method is to quantify capability using a Z metric.  Or for a more detailed perspective, a control chart shows capability over time.  Bottom line: the method you select should fit the level of analysis and level of communication needed for the situation at hand.

Introducing Six Sigma to an Organization

Newbie said,
May 27, 2007 @ 10:46 pm

For an organization not ready yet for the rigor of Six Sigma, what do you suggest for more of a workout approach?

For an organization that says they’re not ready for the rigors of Six Sigma, I’m not apologetic. I tell them the rapid, planned, quantifiable returns of Six Sigma are reserved for those that are ready to take on the raised level of required discipline. That’s the organization’s choice. But let me put this in context: I strongly believe Six Sigma is NOT the appropriate starting point for most organizations. Even if they’re not ready for the rigor of Six Sigma, they still desire organization-wide improvement. As such, I usually introduce Lean to companies first”which is something every company should be doing. There is no better practical and cultural foundation for sustained improvement than Lean. Then when isolated pockets in the organization or the organization as a whole is ready for more rigor (and more return), I introduce them appropriately to Six Sigma. But if the organization’s reception of Lean is lukewarm or the desire for improvement turns out to be localized, I scale back to a targeted workout approach.

Recent Cynicism Toward Six Sigma

Ron said,
May 26, 2007 @ 12:30 pm

Craig, as a MBB myself (and former Motorolan) I wonder if you could comment on the recent struggles Six Sigma has met in the mainstream media¦ it seems everyone from Qualpro to Dilbert is on the witch hunt. I am interested in your thoughts.

Persistent excellence places you in some peoples’ crosshairs”just ask the New York Yankees! I actually take this type of sniping, like from Mr. Adams (Dilbert), as a compliment; for the most part it’s good natured ribbing which confirms the speaker recognizes Six Sigma’s leadership position. At the same time though, there definitely are individuals and organizations within the realm of Six Sigma whose message or tactics provide justification for cynicism. I cringe at some of the stories I hear from the trenches. In the end, I try to value the Voice of the Customer”whether flattering or not”and use that as data to improve.

Stay tuned…more tomorrow.