So you've heard of six sigma but you don't know what it is: here are the answers to many of the questions you might need to have answered.

So you've heard of six sigma but as far as you can see it's just a mass of statistical analysis and data: read this book and learn that it's a lot more than that.

This table is the fascination built into six sigma for me:

Probability of defects of different sigma levels
Sigma Level (Process Capability)	Defects per Million Opportunities
2	308,537
3	66,807
4	6,210
5	233
6	3.4

You do need to understand such things as standard deviations to appreciate this table (see my page on standard deviations for help!)

What that table shows you, though, is this: if you take care of quality and so on at a fairly easy, low level (just within two standard deviations) then for evey one million units or events, there is the possibility that there will be 308,537 rejects.

On the other hand, if you aim at controlling your operations at the level of six sigma, then there should be no more than 3.4 rejects per million.

That might still be an abstract idea for you so read this book and read the author's example relating to six sigma and airline baggage handling ... you'll soon see the relevance of the idea!

Black belts and Green belts: this is an idea that had me puzzling when I first started to learn about six sigma. Is six sigma based on people fling long chopping their way to quality perfection?! Not at all: six sigma embodies the fundamental improvement and development idea which is that if the person at or near the top of the organisation doesn't believe in something then that something just won't work. In my own cost systems work, I always start at CEO level and determine their commitment. If the CEO doesn't like it, no one else will.

So black and green belts are otherwise known as champions: people at or near the top of the organisation whose job it is to lead and drive the six sigma system. Not just rubber stamping; but someone whose job it really is to make it work.

The contents page of this book reads like this:

1. what is six sigma
2. why do six sigma
3. setting business metrics
4. implementing six sigma
5. roles and responsibilites
6. the core of six sigma
7. quick overview of six sigma tools
8. selecting six sigma projects
9. how to sustain six sigma
10. six sigma proof positive

There: isn't that all you need to know? The author is keen for us to know that six sigma is more of a set of ideas and philosophies than just a set of statistical analyses: much more than total quality management too.

That's not to say that statistics and statistical analysis isn't important, it is, they are; and this book does introduce such tools (chapter 7) as

• process mapping
• XY matrix
• multivariate studies
• failure mode effect analysis

Greg Brue has written a good quality introduction to six sigma: it really is raedable and it contains a large number of tables, diagrams and real life examples that will help even the most timorous reader to get to grips with something that companies such as Motorola claim has saved them billions of dollars over a ten year period.

• at General Electric, six sigma added more that $2 billion to the bottom line in 1999 alone;
• Motorla saved more than $15 billion in the first ten years of its six sigma efforts;
• AlliedSignal reports saving $1.5 billion through six sigma.

See, it's a powerful set of ideas and unlike many management fads, along the lines of those touted by people like Tom Peters, six sigma is real, long lasting and valuable.

There you are: follow what Greg Brue has to say and it will lead you into greater things and who knows, maybe you will learn to become a statistical genius at the same time.

Duncan Williamson
17 July 2004