WW 2011, Day One: Error Rates and Sigma-metrics

Posted by Sten Westgard, MS

The Westgard Workshops 2011 were held in Madison, Wisconsin last week, June 1st through 3rd.

Dr. Westgard discusses a question with participants

The topic for the first day was Six Sigma Metrics and Tools. Six Sigma is well known even in healthcare. We did our first Six Sigma workshop about a decade ago. But some of the calculations and implications of Sigma-metrics, particularly for analytical performance, remain less well known. We covered not only the calculations but also the outcomes - how it can improve QC, reduce repeats, increase error detection, and provide better reporting advice to clinicians.

But even beyond these benefits of Sigma-metrics, there's a simple advantage to using the Sigma scale when discussing errors.

Workshops Participants, hard at work

When we talk about error rates, such as a 1% error rate in a process, we intuitively think in personal terms. For example, if you think about a 1% error rate, then you probably also think that you have a 99% chance of missing that error. When you think in these personal terms, you become more willing to accept risk, because you also only think about the risk in terms of a single event.

The Sigma Scale, on the other hand, forces you to think in terms of the whole system. The goal is Six Sigma, which is just 3.4 defects per million opportunities. In other words, a focus on Six Sigma helps drive you to accept less error in the system. Personally, you might think your odds are good with a 4 or even a 3 Sigma process (between 1% and 7% error rate). But when you focus on the system, you realize that those errors happen to someone. It's not who gets "lucky" that matters, but the fact that so many times people will be "unlucky."

Speaking of lucky, we were again fortunate to have good weather on the opening day of the lecture, which meant we could bring some of the participants out to the Memorial Union Terrace. A signature of the workshops is the opportunity to sample Wisconsin's great local beers.

Workshop participants, hard at play.

Dr. Westgard with Michael Xu, a workshop participant from Canada. The educational content was good, but the beer was better.