Cheat Sheet: Six Sigma

Six Sigma? All Greek to me...
Very funny.

Why the six, why the sigma?
It's a statistical term. (You'll find 'sigma' in all manner of standard deviation calculations - or, for the less mathematical, the capital sigma is that sign in Excel that adds everything up.) It refers to instances of defects in a production or services environment - usually relating to a process - such as that there are no more than 3.4 defects per million instances. Five or four sigma would be higher levels of defects but six is the standard.

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And the point of that is...?
Well, it's a quality assurance methodology employed by plenty of companies, in all sorts of sectors. Take manufacturing. If you have to make sure only so many products have problems, running your ops in line with Six Sigma standards is a way of benchmarking what you do. If you ship a million widgets and know no more than three or four have defects, that is helpful, though clearly in many industries even that is too high a failure rate.

Who had this bright idea?
Well, this is an area that professionals and academics spend many hours honing and studying. I wouldn't want to give credit where it isn't due but many look to Motorola as pioneering this approach in the 1980s. Many other industrial big boys have introduced the approach, perhaps most notably GE. Most agree it's a matter of applying quality-assurance approaches that have been out there a while.

And the point is what?
The idea is that customer satisfaction improves and, ultimately, the profits of the company using Six Sigma go up.

Why is this a big deal for IT?
Don't let the Motorola namecheck confuse you. There are two sides to the answer here and a Motorola would sit on both. First, IT vendors, especially hardware manufacturers (though there is definitely a role for it in software development too), use Six Sigma. They don't want faulty products or goods turning up DOA at partners or customers so high-quality production is a must.

At the same time, all the big boys in tech understandably promise that their wares help user organisations achieve Six Sigma quality levels - or higher.

You mentioned this isn't just about manufacturing or products?
No, that's where we hear about it most. But Six Sigma can be applied to a service.

Example...
Take an internet connection. The uptime you could expect could be in line with Six Sigma metrics.

But it isn't.
No, not normally.

I bet I know why...
...You're going to say one of two things. Either service providers will tend to use other terminology, such as 'four nines' or 'five nines' uptime - as in 0.9999 or 0.99999 - at least in terms of measurement, if not methodology. Or no one is rightly going to promise Six Sigma for something as up and down as that. Or five nines, for that matter.

(For the record, Six Sigma works out to 1 minute 47 seconds of downtime per year, in total, while five nines is 5 minutes 15 seconds, assuming a 365-day year.)

How detailed does Six Sigma methodology get?
Very. This Cheat Sheet isn't the place to go for depth. (Hey, it's a cheat sheet.) But we can tell you that there are key stages. The very top line goes like this:

Define - Measure - Analyse - Improve - Control

There then follows a lot of detail, not all of which is straightforward or unconventional. So that's just a teaser for you.

Great. Where do I go for more info?
There is plenty on this out there. Wikipedia is very good as is this site (containing a nice 'Is Six Sigma hype or truth?' poll, I couldn't help notice), which comes with its own 'What is Six Sigma?' definition page. GE has also made a fist of it here .

You some kind of Six Sigma master?
No. But, since you mention it, they are out there and go up in three levels: Green Belt, Black Belt Practioner and Master Black Belt. So don't go joking about the whole martial arts thing.